eChapters

F- distribution : A probability density function that is used in analysis of variance and is a function of the ratio of two independent random variables each of which has a chi-square distribution and is divided by its number of degrees of freedom.

F₀ value : It is used to express F-value when z =10^ºC/18^ºF and the temperature is 121.1^ºC. It is the number of minutes at a specific temperature (250^ºC) required to destroy or kill a stated number of microorganisms and has specific z-value. It is also called reference value. 

Fº value: It is used to express F-value when z =10ºC / 18ºF and the temperature is 121.1ºC. It is the number of minutes at a specific temperature (250ºC) required to destroy or kill a stated number of microorganisms and has specific z-value. It is also called reference value. 

F : Symbol for a generation; F₁ the first generation of a hybrid; F₂ the second; and so on.

F1 : The first filial generation of a cross between two individuals; parental generation (P₁) from which experiment starts.

F2 : The second filial generation of a cross between two individuals; the offspring resulting from crossing the members of the F₁ among themselves.

Flayer: The fragmentation layer in the forest floor, immediately below the litter layer, composed of fragmented, partially decomposed organic materials that are sufficiently well preserved to permit identification as to origin.

F    :    Faraday constant. OR Food - represents BOD in the F/M ratio. Expressed in pounds.

F factor    :    The fertility factor, a plasmid that carries the genes for bacterial conjugation and makes its E. coli host cell the gene donor during conjugation. OR A large bacterial plasmid, known as the sex-factor plasmid because it permits mating between F+ and F- bacteria. 

Fahrenheit Temperature Scale : A temperature scale having freezing point of water as 32 degrees and the boiling point equal to 212 degrees at standard atmospheric pressure. 
    Degree F = (Degree C x 1.8) + 32
    Degree C = (Degree F - 32)/1.8

Fair Weather : Fine sky. Appearance of cirrus or cumulus cover is in fair amount but not covering the sky totally.

Fetch : The distance over which a wind of nearly constant direction has blown, usually over a consistent surface such as water or a forest or a field. Most often the fetch is applied to a distance over water and used to determine the height of wind-generated waves.
 
Fine Weather : A blue and cloudless sky. Even if a few cirrus clouds are noticed, they do not express any vertical development.

Gain threshold: The beginning point of economic damage, expressed in amount of harvestable produce; when cost of suppressing insect injury equals money to be gained from avoiding the damage.

Galea: The lateral lobe of the maxillary stipes; tonguelike, distal lobe attached to the stipes of the maxilla; an apical lobe of the maxilla of an insect; the outer two-jointed lobe of the “pincers” present on the maxilla of insect mouthparts; in adult Lepidoptera the two are joined and enlarged to form the proboscis. (Fig. 63)

Gall: Swellings, deformities, or growths of plant tissue that result from the activities various types of pests, including bacteria, nematodes, mites and insects; an abnormal growth of plant tissues, caused by the stimulus of an animal or another plant (Fig. 128).

Gallicolous: Living in a plant gall either as the producer or inquiline.

Gadget: A slang word applied to any small, handy appliances or devices.

Gagging tape: A metal measuring tape used to determine the depth of liquid in a tank.

Gal.: The unit of acceleration in the centimeter-gram-second system, equal to 1 centimeter per second square; commonly used in geodetic measurement. Formerly known as Galileo, symbolized as Gal.

Galling: A characteristic of metals, which causes them to seize when, brought into intimate contact with each other. A material, which is subjected to galling, is one, which will seize or ‘freeze’ when brought into close contact with like material under pressure and no lubricant.

Gallows plough: An animal-drawn plough, the end of the beam rests freely on a bolster fixed to two front wheels, which is drawn through the front wheel assembly.

Galvanic corrosion: The accelerated corrosion of one metal when it is connected with a more noble metal, e.g. if steel and copper are connected together in seawater, the steel will suffer accelerated corrosion and the copper will be protected.

Galactan : It is a polysaccharide in which major monosaccharide subunit is galactose and often found among the pectic substances of cell walls.

Galactoblast : It is also called colostrums. It is female’s first milk after parturition.

Galactometer : It is an instrument used for recording the specific gravity of the milk.

Galactorrhea : A spontaneous flow of milk from the nipple is called galactorrhea.

Galactometer: It is an instrument used for recording the specific gravity of the milk.

Galactose: It is an aldohexose sugar obtained by hydrolysis of lactose.

Galactosidase: An enzyme (actase) that hydrolyzes a galactoside.

Galactoside: A glycoside that yields galactose on hydrolysis.

Galactosyl: A glycosyl radical C₆H₁₁O₅ that is derived from galactose.

Game: A species of wildlife hunted or trapped by humans, including upland birds, waterfowl, small game, forbearing, and larger mammals that are within the purview of management.

Gamete: i) A mature sex cell, such as sperm/egg used in fertilization. A reproductive cell whose nucleus and often cytoplasm fuses with that of another gamete during fertilization resulting in the formation of a zygote. Gametes are usually differentiated into male and female gametes. ii)  A male or female reproductive cell, typically the product of meiosis, capable of uniting in the process of fertilization with one of the opposite sex.

G    :    Gibbs free energy OR Guanine.

G proteins    :    G proteins are intracellular proteins that bind GTP and convert it to GDP in the process of cell signal transduction. There are two kinds of G protein, the heterotrimeric (α,β, γ) receptor-associated G proteins, and the small G proteins, such as Ras and Raf, that act downstream of many transmembrane signaling events.

Gale : Wind of force 8 or above blowing continuously and damaging trees, houses etc.

General Circulation : The average general distribution of wind in motion on the Earth. This general circulation includes the scientific description of atmospheric dynamics not only statistically but also from the point of view of physics. The global wind systems like westerlies, trades, etc., are the examples of general circulation.

General Circulation Model : At present, there are different models in vogue, to explain the general circulation of the atmosphere. If the general circulation is modelled in a three dimensional procedure, then it is known as a general circulation model.

Geopotential : The potential energy per unit mass of a body due to the earth’s gravitational field referred to an arbitrary zero.

Hard pesticide: One which persists for a long time in the environment; particularly applies to organochlorine insecticides.

Habit, Habitus: The general appearance of an organism; facies.

Habitat modification: Alteration of the environment where an organism occurs, e.g., cultivating land for agriculture.

Habitat: The environmental conditions and associated organisms that occur in a particular site; the place where plants and animals live, usually with a distinctive boundary (e.g. field, pond, sand-dune, rocky crevice); the natural or usual dwelling place of an individual or group of organisms. (L. habitus = condition).

Habituation: A form of associative learning in which a given stimulus no longer elicits a response; learning not to respond to a stimulus that provides no reward or punishment.

Habituation: Reduction in the response to a stimulus with repeated exposure, through modification of the central nervous system.

Haematophagous: Blood-sucking; blood –feeding.

Haemocoel (also hemocoel): The main body cavity of many invertebrates, including insects, formed from an expanded ‘blood’ system that is filled with blood (haemolymph) within which the internal organs lie.

Half round file: A file, which is flat on one side and curved on the other. The amount of convexity never equals a semicircle.

Half section: In mechanical drawing, a sectional view that terminates at the centreline, showing an external view on one side of the centerline and on the other side an interior view.

Hammer: An instrument or tool used for striking blows in metalworking, driving nails, etc. Hammers are of various kinds, each bearing a name according to the purpose it has to serve.

Hammer mill: 1. A type of impact mill or crusher in which materials are reduced in size by hammers revolving rapidly in a vertical plane within a steel casing. Also known as beater mill. 2. A grinding machine, which pulverizes feed and other products by several rows of thin, hammers revolving at high speed.

HACCP : The Hazard Analysis and Critical Control Points (HACCP) is a scientific, rational and systematic approach to identify, assess and control hazards during production, processing, manufacturing and use of food. It ensures safety of the food. HACCP presents a good opportunity for the food industry for upgrading quality and bringing uniformity and consistency in their supplies to international market. or It is a systematic preventive approach to food safety that addresses physical, chemical and biological hazards as a mean of prevention rather than finished product inspection. It involves identification, evaluation and control of hazards which are significant for food safety.

H layer: The humus layer of the forest floor, consisting largely of well-decomposed, amorphous organic matter.
 
Habitat: i) The sum of effective environmental conditions under which an organism lives. ii) Often used for the natural range of distribution of a species. iii) The kind of place in which a plant or animal lives, such as forest habitat, grassland habitat etc. iv) The ecosystem in which a plant or animal lives and obtains food and water. v) It refers to a place or ecological community, or a set of ecological communities, in which an organism or population of organisms occurs. vi) The immediate environment occupied by an organism. vii) The natural environment of an organism excluding other living organisms (the biotope). See also Site. viii) The place or environment where an animal (or plant) naturally or normally lives and raises young.

H    :    Hour.

H    :    Planck’s constant.

H antigens, histocompatibility antigens   :    H antigens or histocompatibility antigens, are known as major histocompatibility antigens when they encode molecules that present foreign peptides to T cells and as minor H antigens when they present polymorphic self peptides to T cells. See also histocompatibility.

Haboob : Sudanese name for duststorm or sandstorm with strong winds that carry small particles of dirt or sand into the air, particularly severe in areas of drought.
 
Habitat : A place where a plant or a community of plants or a crop is existing.

Hadley Cell : A mean thermally driven atmospheric circulation in which warm air rises and flows away from the equator at upper level and descends at the tropics. Wind moves from the tropics back to equator poleward. In many cases this term is also referred to as ‘Hadley circulation’.

Hail : Solid precipitation in the form of balls or pieces if ice (hailstones) with diameter ranging from 5 mm to 50 mm or even more. 
Hailstorm : A storm, often too long and severe, consisting largely of hail or frozen rain drops ranging in diameter from 5 mm to 10 mm or more. 

Ichthyology: Science dealing with the study of fishes – a class of aquatic vertebrates most of whom depend for respiration exclusively on oxygen dissolved in water (Gr. ichtys = fish + logos = study).

Idiobiont: A parasitoid that prevents its host from developing any further, by paralysis or death; see also Konobiont.

IGR: See insect growth regulator

Ileum: The second section of the hindgut, preceding the colon differentiated region of the anterior intestine of the hindgut preceding the rectum in some insects (Fig. 120).

Imaginal buds: See imaginal disc.

I beam: A steel beam shaped like the letter I, used in structural work.

I. H.P. (Indicated Horse Power): ‘Pure’ horse power as measured in the combustion chamber before friction and other loses are subtracted.

IC Engine (ICE): Internal Combustion Engine.

Ideal compression-compression refrigeration cycle: completely vaporizes the refrigerant before it is compressed and expands the refrigerant with a throttling device, such as an expansion valve or capillary tube. The compression-compression refrigeration cycle is the most widely used cycle for refrigerators, air-conditioning systems, and heat pumps. It consists of four processes:l- 2 Isentropic compression in a compressor; 2-3 Constant- pressure heat rejection in a condenser; 3-4 Throttling in an expansion device; 4-1 Constant-pressure heat absorption in an evaporator

Ideal cycle: is an actual cycle stripped of all the internal irreversibilities and complexities. The ideal cycle resembles the actual cycle closely but is made up totally of internally reversible processes.

Ideal gas: Is a gas that obeys the ideal-gas equation of state.

ICAP : It stands for International Centre for Alcohol Policies.

Ice Bank Cooler : Air forced cooler leads to desiccation of the produce. So use forced air high humidity cooler are known as Ice Bank Cooler. Ice bank Coolers are useful for strawberry.

Ice bank cooling : Storing of fruit and vegetable in storage chamber with positive ventilation and a system countries where ice formation is allowed during night time (as electricity cost of night is less as compared to the day time). Melting of ice occurs during day time and with proper air circulation by means of ventilation process, approximately 0.5-1^ºC temperature with 90% RH in the chamber is maintained.

Ideotype: A conceptual model of a plant type that will be best suited to a particular set of circumstances. Ideotypes can be defined in terms of both form and function. There can be ‘isolation’, ‘competition’ and ‘crop’ ideotypes.
Illuvial horizon: i) A soil layer in which material from above has been deposited; the layer of accumulation. ii) A soil horizon that receives material in solution or suspension from some other part of the soil. See also Eluviations.
Image: Picture or graphical representation. In remote sensing and GIS as a term that describes digital representations of earth features (TWS).

I&D    :    Incision and drainage.     
I&E    :    Internal and external.     
I&O    :    Intake and output.     
I.P. (IP)    :    Intraperitoneal .    
I.V. (IV)    :    Intravenous.

Ice Caps : A perennial ice/snow cover over an extensive area of land or sea, found only around the two geographic poles.

Ice Columns : Ice crystals resembling stubby pencils rather than the delicate branched snowflake shape. Columns typically form in the temperature ranges -5° C to -8° C (23° F to 18° F) and below -25° C ( -13° F). They are long in comparison to their hexagonal cross-section.

Ice Crystals : 1) Hexagonal (6-sided) crystals that form upon freezing of water, may be in one of several shapes : stars, needles, plates, columns or combinations of these forms. 2) Precipitation in the form of slowly falling, singular or unbranched ice needles, columns, or plates, may be called diamond dust.

Ice Fog : Fog composed of minute ice particles that occur in very low temperatures (typically - 30°C or - 22°F & below) under clear, calm conditions in the polar latitudes. 

Jet: Liquid emitted from a nozzle orifice (in USA = nozzle).

JH: An abbreviation of juvenile hormone.

Johnston’s organ: A sense organ similar to a chordotonal organ, located in the second antennal segment of most insects; functions in sound reception in some Diptera (Fig. 153); an organ in the pedicel of the antenna, consisting of a cluster of chordotonal sensilla.

Jack, electric: A form of metallic spring contact, connection being made by inserting a plug, which is attached to a cord. Commonly used on telephone switchboards and radios.

Jack, hydraulic: Device for raising weight or exerting pressure by pumping oil or other liquid under a piston or ram.

Jack: A mechanical device used for lifting heavy loads through short distances with a minimum expenditure of manual power.

Jacket: An outer casing, as around a boiler or tank, to preserve heat or cold, or around a motor cylinder, permitting a flow of water to prevent overheating.

Jacking up: The raising up of masses of machinery and heavy structures by means of jacks.

Jackscrew: Small screw jacks for leveling work in jigs.

Jaboticaba : It is a Brazilian tree (Myrciaria cauliflora) of the myrtle family cultivated in warm regions for its edible purplish fruit.

Jack salmon / walleye : A large vigorous American freshwater food and sport fish (Stizostedion vitreum) that has large opaque eyes and is related to the perches but resembles the true pike sometime also called walleyed pike

Jaggery : Raw brown / unrefined brown sugar in lump made from palm sap.

Jalshakti: It is a material (starch based polymer) which can absorb and hold 80-100 times its weight of water. It is a gel on which plant roots lock themselves and tap the water. It can be used on most soils and in all composts to promote vigorous growth and minimise plant stress. It is used by mixing with growing medium at the rate of 1-2% by weight. Plant roots attach themselves to hydrated granules of the chemical and tap their water store. Jalshakti reduces watering needs.

Jam: Concentrated fruit pulp with natural fruit flavour where pectin imparts a good set and high sugar concentration (68%) facilitates its preservation.
 
Jungle: The general Indian term for forest.

J    :    Joule.

J    :    Joining segment.

J chain      :    A polypeptide present in polymeric IgM and IgA that links the subunits together.
    
J gene segments, joining gene segments     :    The J gene segments, or joining gene segments, are found some distance 5' to the C genes in immunoglobulin and T-cell receptor loci. A V and in the case of IgH chains, tcrâ chains and tcrä chains, a D gene segment must also rearrange to a J gene segment to form a complete V-region exon.

January Thaw : A period of mild weather, usually following a cold spell, which often occurs in late January in the eastern regions of North America, particularly around the Great Lakes region, New England and the Canadian Maritime Provinces. The thaw is associated with a strong flow of warm air northward from the Gulf of Mexico on southerly winds on the back of a high pressure system.

Jet Stream : A relatively narrow band of high-speed winds, generally greater than 50 knots (57 mph or 93 kmph), found in the upper troposphere above regions of strong horizontal temperature contrasts such as fronts. The major jet streams are the subtropical jet and the polar jet stream.

Joule : The unit of work or energy. In mechanical systems, this is the work done when a force of one Newton displaces the point of application by a distance of one metre in the direction of force. In electrical systems, a joule is the equivalent of moving one coulomb through a potential difference of one volt. One joule is equal to one watt per second

Kairomone: A chemical produced by an individual of one species that has a beneficial effect on the recipient individual of another species; a chemical that is adaptively favourable to the receiving organism; an interspecific messenger substance that benefits the receiver but not the releaser (e.g., attractants, excitants); an interspecific chemical messenger that benefits the receiver but not the emitter; a communication chemical that benefits the receiver and is disadvantageous to the producer; see also Allomone; Synomone.

Karyological character: A character involving chromosome structure or number (cf. Taxonomic character).

Keeled: With an elevated ridge or carnia.

Keratin: The inert exoskeleton protein of vertebrate animals forming skin, hair, feathers, claws, nails, scales, etc.; similar in structure and function to the arthropod chitin.

Keratolytic: Pertaining to or promoting loosening or separation of the outer layer of the skin.

Kelvin scale: The thermodynamic temperature scale in the SI and is named after Lord Kelvin (1824-1907). The temperature unit on this scale is the Kelvin, which is designated by K (not °K; the degree symbol was officially dropped from Kelvin in 1967). The lowest temperature on the Kelvin scale is 0 K.

Kelvin unit: magnitude was established at the International Conference on Weights and Measures in 1954. The triple point of water (the state at which all three phases of water exist in equilibrium) was assigned the value 273.16°K (0.01 °C). The magnitude of a Kelvin is defined as 1/273.16 of the temperature interval between absolute zero and the triple-point temperature of water. The magnitudes of temperature units on the Kelvin and Celsius scales are identical (1 K, 1°C). The temperatures on these two scales differ by a constant 273.16.

K ration : It is a lightweight packaged ration of emergency foods developed for the U.S. armed forces in World War II.
Kairomone : A chemical substance emitted by one species and especially an insect / plant that possess an adaptive benefit (stimulus for oviposition) to another species.
Kaiser rolls : A round crusty roll often used for sandwiches.
Kalamata /calamata : It is brine cured black olive grown in Greece.

Kaolinite: An aluminosilicate mineral of the 1.1 crystal lattice group.

Ketchup: Strained concentrated extract of fruit/vegetable which is having spiced vinegar.

Keystone species: i) A species that other species depend upon for survival. ii) A species whose impacts on its community or ecosystem are large, and much larger than would be expected from its abundance. iii) A keystone species is one which has a disproportionately large impact on its ecosystem, and its presence affects many other organisms by helping determine the types and numbers of other species in the community. If a keystone species is removed the delicate balance of an ecosystem would be dramatically changed, and the ecosystem itself could collapse. Important pollinators, such as hummingbirds, bats or butterflies, can be keystone species, as so many other species are reliant on them for survival. Predators such as Jaguar, are often keystone species. Jaguars are present in very small numbers in Central and South America, but they play a critical role in keeping populations of other mammals in check. Identifying and protecting keystone species is important for the long term survival of an ecosystem.

K    :    Kilo (10³g).
 
K    :    Potassium.

KA    :    Ketoacidosis.

Karlvon Baer    :    Person who‚ in 1828‚ published on the developmental stages in mammalian eggs and showed that an undifferentiated‚ single-celled egg grows into a many-celled embryo.

Katabatic Wind : Downslope gravitational flow of the colder, denser air beneath the warmer, lighter air results and comprises the katabatic wind. It is also known as the drainage wind or mountain wind.

Kelvin Temperature Scale : An absolute temperature scale in which the zero point is absolute zero. The scale is based upon the triple point of pure water and the size of the degree is same as on the celsius scale. So the 273.16 K = 0°C. That means the freezing point of water is 273.16 K and boiling point of water is 373.16 K, etc. This is more commonly called as the absolute.

Label: Technical information about a registered pesticide in the form of printed material attached to, or printed on, the pesticide container. It is illegal to use the pesticide in ways inconsistent with the label.

Labella (sing. labellum): In certain flies, paired lobes at the apex of the proboscis, derived from labial palps; apical spongelike structure on the proboscis of nonbiting muscoid flies (Fig. 156).

Labeled: Equipment or materials to which has been attached a label, symbol or other identifying mark of an organization acceptable to the “authority having jurisdiction” and concerned with product evaluation, that maintains periodic inspection of production of labeled equipment or materials and by whose labeling the manufacturer indicates compliance with appropriate standards or performance in a specified manner.

Laboratory: A place where scientific tests, experiments, analysis, etc., are carried on.

Ladder: An aid to climbing. Usually made of two parallel uprights connected by regularly spaced rungs.

Ladle: Receptacle used for taking the molten metal from the cupola, in transporting it, and in pouring it into the molds. Ladles are of various shapes and sizes with capacities from 25 pounds to 100 tons.

L - Ascorbic acid : It is a white crystalline compound with a slightly acidic taste. It is readily soluble in water, alcohol, glycerin, propylene glycol and is insoluble in oils, fats, ether, benzene, chloroform.

Lab coat : A loose white coat with deep pockets that is worn in a laboratory or medical office.

L layer: The litter layer of the forest floor, consisting of unaltered dead remains of plants and animals.

Land : Land is a broader term than soil. In addition to soil, its attributes include other physical conditions such as mineral diposits and water supply; Location in relation centers of commerce, population, and other land; the site of the individual tracts or holdings; and existing plant cover and works of improvement.

Land capability: The suitability of land for use without damage. Land capability (as ordinarily used in the united states) is an expression of the effect of physical land conditions, including climate, on total suitability for use without damage, for crops that require regular tillage, for grazing, for woodland and for wildlife. Land capability involves consideration of the risk of land damage from erosion and from other causes and also difficulties in land use owing to physical land characteristics, including climate.

K    :    Kilo (10³g).

K    :    Potassium.

KA    :    Ketoacidosis.

Karlvon Baer    :    Person who‚ in 1828‚ published on the developmental stages in mammalian eggs and showed that an undifferentiated‚ single-celled egg grows into a many-celled embryo.

Lake Effect : The effect of any lake in modifying the weather and climate along its shore and inland which depends on the size of the lake. In some areas such as the North American Great Lakes, lake effect refers to snowfall generated by the lake on the downwind shore.

Lake Effect Snowfall : Snowfalls along the lee shore of a lake or downwind some distance from the shore caused by the modification of cold, subfreezing air by the relatively warmer lake water. The intensity of the lake-effect snowfall depends upon several factors : the temperature contrast between the lake surface and the air passing over it, the over-water distance the air has traversed (the fetch), and the regional weather situation. 

Macro: Large.

Macro-and microconsumers: In an ecosystem the primary consumers, feed on plants while other consumers, e.g., secondary and tertiary consumers are called macroconsumers. The decomposers, like bacteria and fungi, are called microconsumers.

Macro-and micronutrients: Some salts or elements needed in relatively large amount are termed macronutrients while some others though essential for maintaining the life-system are required in minute amounts and are the micronutrients.

Macroclimate: General climate prevailing over a large area, considered as a unit. The opposite is microclimate.

Macroevolution: Major phylogenetic patterns that develop over wide spans of geological time.

Macrofauna: The larger members of a particular fauna. Open to different levels of interpretation for they may be larger vertebrates or alternatively the larger insects of a habitat. The opposite is microfauna.

Macrogamete: The female gametocyte of a malaria parasite, Plasmodium spp; see also Microgamete.

Macrophage: An eater of large particles; see also Microphage.

M

Mach number: Named after the Austrian physicist Ernst Mach (1838-1916), is the ratio of the actual velocity of the fluid (or an object in still air) to the velocity of sound in the same fluid at the same state.

Machine: 1. A combination of rigid or resistant bodies having definite motions and capable of performing useful work. 2. A device for transforming or transferring energy.

Machine drawing: A mechanical drawing of a machine or machine parts provided with notes and dimensions for workshop information.

Machine drilling: The d rillin g of work under a power-driven machine.

Machine molding: The use of special machines in the preparation of molds for the production of castings.

Machine rating: The amount of power a machine can deliver without overheating.

Machineable: Material capable of being finished by tools or cutters in or on a machine tool.

Machinery: A group of machines; also, the working parts of an engine or machine.

Machining: Performing various cutting or grinding operations on a piece of work.

MAC : It stands for modified atmospheric coating.

Macaroni : Pasta made from semolina and shaped in the form of slender tubes.

Macaroni wheat : It is tetraploid wheat and is preferred for making macaroni, vermicelli etc.

Macaroon : A small cookie composed chiefly of egg whites, sugar, and ground almonds or coconut.

Mace : An aromatic spice consisting of the dried external fibrous covering of a nutmeg.

Macroclimate: The climate of a region. See also Microclimate, topoclimate.
Macronutrient: A chemical element necessary in large amounts (usually > 50 ppm in the plant) for the growth of plants. Includes c, h, o, n, p, k, ca, mg, s. ‘Macro’ refers to quantity and not to essentiality of the element. See also Micronutrient.
Maggot: Legless larva, especially of a fly.
Main effect: The response to different levels of a treatment factor, measured independently of other factors. In a balanced design such as a randomized complete block, the main effects of levels of a treatment factor are estimated by averaging the corresponding responses over all levels of every other factor.

M    :    Milli (10^-3l).

M    :    Molar (mol/L).

M    :    Microorganisms - small organisms which require a microscope to be seen. M represents the SS in the mixed liquor and is part of the F/M ratio. 

Macroclimate : It deals with the study of atmosphere over large areas of the earth and with the large scale atmospheric motions that cause weather. It helps in forecasting weather. OR Climate of a continent or over the complete globe.
 
Macrometeorology : A branch of meteorology concerned with the study of large scale meteorological phenomena over a continent or the entire globe.

Macroscale : The meteorological scale covering an area ranging from the size of a continent to the entire globe.
 
Marine climate : Almost similar and on many occasions used as a synonym to maritime climate. The climate is basically influenced by adjacent seas and oceans.
 
Maritime Climate : The climate experienced in areas and regions near the oceans and seas. It is characterised by hot dry summers and mild wet winters. The diurnal variations of temperature are small and air is with high relative humidity.

Naiad: The immature stage in insects with incomplete metamorphosis that feed and develop in water; an aquatic, gill-breathing, immature instar of hemimetabolous insect.

Narcotic: A chemical that causes reversible depression of the nervous system.

Narrow spectrum (as applied to insecticides): Having an effect on only a narrow range of insects.

Nasus: A nose, the snout of certain termite soldiers (nasutes).

Nasute (pl. nasuti): A type of soldier caste in certain termites; this form bears a median frontal rostrum or snout through which it ejects a defensive fluid; the jaws are small or vestigial.

Nasutus (pl., nasuti): An individual of a termite caste in which the head narrows anteriorly into a snoutlike projection.

Natality: Population ‘increase’ factor; birth rate; often measured as total number of eggs or eggs per female per unit of time.

Natural gas: Produced from gas wells or oil wells rich in natural gas. It is composed mainly of methane, but it also contains small amounts of ethane, propane, hydrogen, helium, carbon dioxide, nitrogen, hydrogen sulphate, and water vapour. It is stored either in the gas phase at pressures of 150 to 250 atm as CNG (compressed natural gas) or in the liquid phase at 162° C as LNG (liquefied natural gas).

Natural-draft cooling tower: Uses the naturally occurring density gradients between the inside air-water vapour mixture and the outside air which create an airflow from the bottom to the top of a wet cooling tower.

Needle valve: A valve in which the flow of liquid or gas is regulated by the adjustment of a pin or needlepoint, which sets in a cone-shaped depression having a small hole at the bottom.

Negative: One of the two terminals in an electrical circuit, presumably the one through which the current returns to the source.

Negative camber: The condition existing when two tyres are closer together at the top than at the bottom.