Why do Verbs after modals not take the third person singular s.?

You're right! Verbs after modals don't take the third person singular "-s". Here's why:

* Modals express possibility, ability, necessity, or permission. They are auxiliary verbs (helping verbs) that help the main verb convey these ideas. Examples include: *can*, *could*, *may*, *might*, *must*, *should*, *will*, *would*.

* The third person singular "-s" is an inflection that marks the present tense, simple form of a verb. It's used to show that the subject is a singular noun or pronoun in the third person (he, she, it).

* Modals already indicate present tense. They don't need an additional "-s" to show this. The main verb after the modal is considered part of the verb phrase, not a standalone verb in the simple present tense.

Here's a breakdown:

* Correct: He can *swim*.

* Incorrect: He cans *swim*.

In the incorrect example, the "-s" is unnecessary because *can* already indicates present tense and "swim" is part of the verb phrase.

Think of it this way: the modal verb is the "boss" and tells the main verb what to do. The modal says, "I've got the present tense covered!"

Let me know if you have any other questions!