A contest is a struggle to win power or control especially in politics.
1. …the contest for the deputy leadership of the Labour Party.
A contest or competition is an event in which people take part in order to find out who is the best at something, especially in order to win a prize. They usually involve tests of knowledge, speed, skill, or talent.
2. The local radio station was sponsoring a contest to find the most popular high school athlete.
3. Her insurance company employers held sales contests for its staff, with merchandise prizes.
4. She won several competitions for rock-and-roll dancing.
5. …a magazine full of competitions and activities.
If only two people are involved, you usually use contest. For example, if you are talking about an event in a sport such as boxing or wrestling, you refer to it as a contest.
6. …the heavyweight contest between Muhammad Ali and the Canadian champion Trevor Berbick.
A competition is often more serious than a contest, with more complicated rules or more complicated things to do. It may take place over a longer period of time, and the entrants may have to do several different things.
7. …the 1981 Lorry Driver of the Year competition.
8. His greatest disappointment was that he didn’t win the competition to do the Byron memorial in Hyde Park.
Contest is also a verb. If you contest something such as a decision or a will, you object to it formally and oppose it, sometimes aggressively.
9. I am going to contest the will.
10. We would hotly contest this idea.
If parliamentary candidates contest a seat, they try and win it.
11. There was a by-election contested by six candidates.
Competition is used most commonly as an uncount noun to describe a situation in which two or more people or organizations are trying to get something that only one of them can have. When they are in this situation, you can say that they are in competition.
12. As the population expanded, so did the competition for land.
13. Searle is likely to face some stiff competition from Tate & Lyle.
14. The two parties were not in competition with each other.
Note that ‘contest’ is not used in this way.