n. 1
The action of opposing or of being in conflict.
The two politicians are in opposition to the bill.
n. 2
An opposite or contrasting position.
Near-synonym: oppositeness
n. 3
The apparent relative position of two celestial bodies when one is at an angle of 180 degrees from the other as seen from the Earth.

Related words

Forms

Opposition or Competition?

Opposition is becoming a frequent substitute for competition in business language; it implies that the competitor is an opponent and hinderer.

J. C. Fernald, English Synonyms and Antonyms (1914)

Word	1850 → 2019	Trend
opposition		steady
resistance		steady

Use in printed books, per decade from 1850 to 2019.

3 letters: foe¹
4 letters: kick¹
5 letters: stand¹, enemy³
6 letters: rebuff²
7 letters: discord², repulse²
8 letters: opposite³, conflict², contrast², opponent³, defiance³, clashing², acrimony⁴
9 letters: diversity⁴, hostility⁴, animosity⁵, antipathy⁴
10 letters: resistance³, impediment⁴, antithesis⁴, antagonism⁵, repugnance, repellency
11 letters: competition⁴, obstruction³
12 letters: interference⁴, oppositeness
13 letters: confrontation⁴, contradiction⁴, inconsistency⁵, contravention⁴

The small number after each word is its number of syllables (enemy³ = 3 syllables).