‘Competition’ can be countable or uncountable.

Uncountable (=a situation in which people/organisations try to be more successful  than other people/ organizations)

e.g. Young people face increasing competition in the jobs market.

Countable (= an organised event where people compete against each other)

e.g. I won a photography competition when I was a child.

Get more examples here.

Common collocations:

fierce, intense, keen, serious, severe, stiff, strong, tough 

Common mistakes:

There was a fierce competition between Microsoft and Apple.