Review of the Modals

Modals are helping verbs that express special meanings. They all follow these basic rules:

1. They are followed by the base form of the verb (without to).
   For example: I might play football tomorrow.
2. They have the same form with all subjects. (They don’t take s, ing or ed.)
   For example: He could play yesterday.
3. They form questions and negatives without helping words (do, does, did, didn’t, will, etc.).
   For example: He shouldn’t go there.
One-word modals invert (change places) to form yes/no questions.
For example: Can they sing?
4. The same modal can have many meanings.

Semi-Modals

Some modals don’t follow all of the rules. They are called semi-modals. (be) supposed to, be able to and have to are semi-modals.
Like full modals, they are followed by the base form of the verb. Unlike full modals:

1. They form questions and negatives with helping words (do, does, did, will, etc.).
   For example: Did you have to work so late last night?

   She isn’t be able to sing very well.
2. He/She/It takes a different form in the present and past tenses.
   For example: I have to do my homework. He has to do his homework.

   He wasn’t supposed to eat your birthday cake.
   They weren’t supposed to eat your birthday cake.

For more information about modals, see:
L2U2L4– have to
L2U3L2– must / mustn’t / polite expressions
L2U4L3– may / might / be supposed to
L2U4L4– should / ought to / had better

In the following table, we see the main meanings of modals. Notice the different ways to express similar ideas.