Simple:
* The children entered a contest to design the best superhero costume.
* The company held a contest to win a free trip to Hawaii.
With different meanings:
* The team contested the referee's decision, arguing it was unfair.
* The lawyer contested the validity of the will.
* The two countries contested control of the disputed territory for decades.
Figurative:
* The artist contested the boundaries of traditional art with his innovative techniques.
* The political candidate contested the election results, claiming fraud.
Choosing the right word:
* If you mean an event with competition, use "contest".
* If you mean to challenge or dispute something, use "contest" as a verb.
Remember to consider the context of your sentence and choose the meaning of "contest" that best fits your meaning.