DEFINING RELATIVE CLAUSES A. You may reduce the restrictive relative if 1. the relative clause consists only of the relative pronoun, the verb to be, and one or more prepositional phrases; A gill is an external respiratory organ which is in the gill chamber at the rear of the mouth of most aquatic animals. —» A gill is an external respiratory organ in the gill chamber at the rear of the mouth of most aquatic animals. Enamel, in dentistry, is a hard, white inorganic material that is on the crown of a tooth. —» Enamel, in dentistry, is a hard, white inorganic material on the crown of a tooth. 2. the relative clause consists of a passive verb plus some additional information; A theater is a building which has been specifically designed for dramatic performances. —» A theater is a building specifically designed for dramatic performances. A collagen is a white, inelastic protein that is formed and maintained by fibroblasts. —» A collagen is a white, inelastic protein formed and maintained by fibroblasts. 3. the relative clause contains the relative pronoun, an adjective ending in -ble, plus additional information. A robot is a multiprogrammable device which is capable of performing the work of a human. —» A robot is a multiprogrammable device capable of performing the work of a human. 4. the relative clause contains the verb have. In this case the relative pronoun and have can both be dropped and replaced by with; A parliament is a national governing body which has the highest level of legislative power within a state. —» A parliament is a national governing body with the highest level of legislative power within a state. 5. the relative clause contains an active state verb (a verb that expresses a state or something that is going on). The relative pronoun is dropped and the verb changed to the -ing form. Exceptions to this are to be and have. Pollution is a form of contamination that often results from human activity. —» Pollution is a form of contamination often resulting from human activity. A moon is a natural satellite which orbits around a planet. —» A moon is a natural satellite orbiting around a planet. Exercise I: Edit the following by reducing the relative clauses 1. Aluminum is a lightweight metal that is often used for hightension power transmission. 2. Heat is a form of energy which can be transmitted through solid and liquid media by conduction. 3. A brake is a device that is capable of slowing the motion of a mechanism. 4. A dome is generally a hemispherical roof which is on top of a circular, square, or other-shaped space. 5. Snow is a form of precipitation which results from the sublimation of water vapor into solid crystals at temperatures below 0°C. 6. An antigen is a substance which causes the formation of antibodies, the body's natural response to foreign substances. 7. A catalyst is a substance that can speed up the rate of a chemical reaction without changing its own structure. 8. A black hole is a celestial body which has approximately the same mass as the sun and a gravitational radius of about 3 km. B. Now notice also that in a full relative clause, the relative pronoun can be preceded by a preposition. The relative pronoun which must be used in this type of restrictive relative clause. This construction is common in formal academic writing. These clauses cannot be reduced. e.g.: A foundation is a base on which a structure can be built. Exercise II: Complete the following definitions by inserting an appropriate preposition. 1. A thermometer is an instrument ___ which temperature can be measured. 2. Photosynthesis is a process ___ which sunlight is used to manufacture carbohydrates from water and carbon dioxide. 3. An anhydride is a compound ___ which the elements of water have been removed. 4. An eclipse is a celestial event __ which one body, such as a star, is covered by another, such as a planet. 5. An axis is an imaginary line ___ which a body is said to rotate. Whereby is commonly used in formal writing instead of by which, by means of which, and through which. e.g.: Collective bargaining is a process whereby employers agree to discuss work-related issues with employee representatives. C. Here are a few final comments on how information should be presented in a one-sentence definition. First, care should be taken to find the precise word or phrase for the class: A microscope is an object . . . , is less precise than A microscope is an instrument. . . A vowel is a sound . . . , is less precise than A vowel is a speech sound . . . Exercise III: Choose a word or phrase that assigns the following terms or phrases to a precise class. Then form their definitions. Use your dictionary, if necessary. 1. a beaker 2. an ellipse 3. an amplifier 4. neon 5. a parasite 6. an electric motor 7. lysine 8. mitosis 9. oxidation 10. (one of your own)