op·po·si·tion 
(ŏp′ə-zĭshən)
(ŏp′ə-zĭshən)n.
1.
a. The act of opposing or resisting.
b. The condition of being in conflict; antagonism: "The history of men's opposition to women's emancipation is more interesting perhaps than the story of that emancipation itself" (Virginia Woolf).
2. Placement opposite to or in contrast with another.
3. Something that serves as an obstacle.
4. often Opposition A political party or an organized group opposed to the group, party, or government in power.
5. Astronomy
a. The position of two celestial objects when their longitude differs by 180°, especially a configuration in which the sun and a superior planet or the moon are on opposite sides of Earth.
b. The position of the superior planet or the moon in this configuration.
6. Logic The relation existing between two propositions having an identical subject and predicate but differing in quantity, quality, or both.
7. Linguistics Contrast in a language between two phonemes or other linguistically important elements.
op′po·sition·al adj.