Hard

Hard is both an adjective and an adverb. When it is an adverb, it means ‘needing or using a lot of physical or mental effort’. It goes after the main verb:

I studied hard for my exams but didn’t do very well.
We have worked hard all day.

The comparative and superlative forms are harder and hardest:

He didn’t get into the team this year. He’ll just have to try harder next time.
Not: ~~He’ll just have to try more hard next time.~~
Right, children, who has worked hardest today?

warning

Don’t confuse hard with hardly. Hardly usually means ‘only just’ or ‘almost not’:

Every day I ran a lot and worked hard so that I would be prepared for the game.
Not: ~~Every day I ran a lot and worked hardly.~~