Noun – Imperative
1 [count] formal : a command, rule, duty, etc., that is very important or necessary
She considers it a moral imperative to help people in need.
2 a grammar term : the form that a verb or sentence has when it is expressing a command
“Eat your spinach!” is in the imperative.
2 b [count] : an imperative verb or sentence
“Go” and “buy” are imperatives in the sentence “Please go to the store and buy some milk.”