noun

 

usual food the type of food that someone usually eats

His diet isn't very healthy.

 

special food when someone eats less food, or only particular types of food, because they want to become thinner, or because they are ill

No cake for me, thanks - I'm on a diet.

 

verb

 

to eat less food so that you become thinner

I've been dieting for a week, and I still haven't lost any weight.