appears as a printed or displayed mark, e.g. one of the letters of the alphabet, a number or a punctuation mark characterisation noun a description of the typical features of something O ecological characterisation of the landscape characterise verb 1. to be a characteristic of something or someone O Deserts are characterised by little rainfall, arid soil and very little vegetation. 2. to describe the typical features of something characteristic noun a property or feature of something O inherited characteristics O One of the characteristics of an octopus is that it can send out a cloud of ink when attacked. ■ adjective typical or special characteristic species noun a species typical of and only occurring in a particular region charcoal noun an impure form of carbon, formed when wood is burnt in the absence of oxygen charge noun a quantity of electricity measured in coulombs chart noun 1. a diagram showing information as a series of lines or blocks 2. a map of an area of water such as the sea or a large lake ■ verb to make a chart of something chasm noun a deep hole in the earth or rock chem- prefix referring to chemistry or chemicals chemical noun a substance formed of chemical elements or produced by a chemical process O the widespread use of chemicals in agriculture O The machine analyses the chemicals found in the collected samples. ■ adjective 1. referring to chemistry or chemicals 2. not found in nature (informal) O an unpleasant chemical taste chemical bond noun the force which links atoms to form molecules. Also called bond chemical closet noun same as chemical toilet chemical control noun the control of pests using chemicals chemical element noun a substance which exists independently and cannot be broken down into simpler substances chemical fertiliser noun same as artificial fertiliser

Chemical of Concern noun » List of Chemicals of Concern chemical oxygen demand noun the amount of oxygen taken up by organic mat ter in water used as a measurement of the amount of organic matter in sewage. Abbr COD

chemical toilet noun a toilet containing chemicals to neutralise the body's waste products. Also called chemical closet chemical toxicity noun the poisonous nature of chemicals used in pest control chemist noun a scientist who specialises in the study of chemistry chemistry noun 1. the study of substances, elements and compounds and their reactions with each other 2. chemical substances existing together O Human action has radically altered the chemistry of the atmosphere.

chemo- prefix chemistry chemoautotrophic adjective referring to the oxidation of nitrogen or other chemical elements to create a source of food. Compare photoautotrophic chemolithotrophic adjective referring to organisms such as bacteria which obtain energy from inorganic substances chemo-organotrophic adjective referring to an organism such as an animal which obtains its energy from organic sources chemoreceptor noun a cell which responds to the presence of a chemical compound by activating a sensory nerve. i> receptor chemosphere noun the zone in the Earth's atmosphere, above the upper part of the troposphere and within the stratosphere, where chemical changes take place under the influence of the Sun's radiation chemosterilant noun a chemical substance which sterilises by microorganisms chemosynthesis noun the production by bacteria of organic material using chemical reactions chemotaxis noun a movement of a cell which is attracted to or repelled by a chemical substance chemotroph noun an organism which converts the energy found in organic chemical compounds into more complex energy, without using sunlight. Compare pho-totroph chemotrophic adjective obtaining energy from sources such as organic matter. Compare phototrophic (note: Most animals are chemotrophic.) chemotropism noun the movement or growth of an organism in response to a chemical stimulus

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