Khan Academy
Khan Academy: Modal Verbs
There's a class of helper verbs known as modals that we use to express a bunch of conditions: we can use them to give advice, make guesses at how necessary or likely something is, make requests of people, and so on. They're super useful.
Khan Academy
Khan Academy: Helping Verbs
We've established that verbs can show actions and link ideas together. Now, let's talk about how some verbs can be used to help other verbs.
Sophia Learning
Sophia: Present Perfect: Lesson 4
This lesson introduces the present perfect tense and how it is used. It is 4 of 4 in the series titled "Present Perfect." [5:08]