—oppositional, oppositionary, adj. —oppositionless, adj./op'euh zish"euhn/, n.1. the action of opposing, resisting, or combating.2. antagonism or hostility.3. a person or group of people opposing, criticizing, or protesting something, someone, or another group.4. (sometimes cap.) the major political party opposed to the party in power and seeking to replace it.5. the act of placing opposite, or the state or position of being placed opposite.6. the act of opposing, or the state of being opposed by way of comparison or contrast.7. Logic.a. the relation between two propositions that have the same subject and predicate, but which differ in quantity or quality, or in both.b. the relation between two propositions in virtue of which the truth or falsity of one of them determines the truth or falsity of the other.8. Astron. the situation of two heavenly bodies when their longitudes or right ascensions differ by 180°: The moon is in opposition to the sun when the earth is directly between them.9. Astrol. the situation of two heavenly bodies or groups of heavenly bodies whose celestial longitudes differ by 180°, conducive to confrontation or revelation: an astrological aspect.10. Elect. the condition that exists when two waves of the same frequency are out of phase by one-half of a period.11. Ling.a. the relationship between any two alternative units within a linguistic system, esp. between minimally distinct phonemes.b. the feature that constitutes the difference between two such units.[1350-1400; < L opposition- (s. of oppositio), equiv. to opposit(us) (see OPPOSITE) + -ion- -ION; r. ME opposicioun < OF opposicion < L as above]
* * *in astronomy, the circumstance in which two celestial bodies appear in opposite directions in the sky. The Moon, when full, is said to be in opposition to the Sun; the Earth is then approximately between them. A superior planet (one with an orbit farther from the Sun than Earth's) is in opposition when Earth passes between it and the Sun. The opposition of a planet is a good time to observe it, because the planet is then at its nearest point to the Earth and in its full phase. The planets Venus and Mercury, whose orbits are smaller than Earth's, can never be in opposition to the Sun.
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