B1
a verb, for example "can," "might" or "must," that is used before another verb to show that something is possible, necessary, etc.
Dictionary examples:
Can you believe it? 'Can' is a modal verb! (0.0)
My teacher said I should use more modal verbs, so I will! (0.0)
I would love to master modal verbs, but it's not easy! (0.0)
The first verb in the following sentence is a modal: We ought to pay the gas bill. (34.0)