Unit 9 (and 10) Grammar: Modals of Necessity “have to” and “must”

What is a modal?• The easy answer: A modal is a special kind of verb!

• There is another verb after a modal verb. This verb is like the dictionary form (base form).

Examples:I must sing.We have to go.This must change.He has to run.

What are modals of necessity?• “Have to” and “must”• These tell us something that is necessary

Sometimes, “have to” and “must” have similar meaning

• “Have to” is usually for conversation.• “Must” is usually for writing.• “Must” is stronger.

Some examples …

Which would be the most normal choice?

Conversation:• I have to go.• I must go.

An academic essay:• People must change their habits to protect the environment.• People have to change their habits to protect the environment.

Some examples …

Which would be the best choice?

Conversation:• I have to go.• I must go.

An academic essay:• People must change their habits to protect the environment.• People have to change their habits to protect the environment.

Conjugation of “have to” vs. “must”• Have to:

I have to We have toYou have toShe has to They have to

• MustI must We mustYou mustShe must They must

What is the difference between these verbs?

“Must”: an unchanging verb!• “Must” is special because it never changes (isn’t that nice?)!

I must study We must study You must studyHe must study They must study

• Must CANNOT be used in the past tense. Instead, use “had to”.WRONG example: We musted go. CORRECT example: We had to go.

Choose “must” or a form of “have to” …Yesterday, I __(1)__________ do homework all day, so I didn’t have time to go to the store. That means that today, I ___(2)_____ go, because I need to buy milk. I ___(3)_______ buy milk because yesterday my roommate ___(4)__________ take a test, and she got a low score. Now she is sad. Her favorite dessert is chocolate chip cookies, so I ___(5)_______ make them for her today to cheer her up.

Choose “must” or a form of “have to” …Yesterday, I had to do homework all day, so I didn’t have time to go to the store. That means that today, I have to/must go, because I need to buy milk. I have to/must buy milk because yesterday my roommate had to take a test, and she got a low score. Now she is sad. Her favorite dessert is chocolate chip cookies, so I have to/must make them for her today to cheer her up.

Practice with a partner• What did you have to do last week? Try to find 5 things you

both had to do! (Remember, you can only use “had to” to speak about the past.)• “Last week, we had to …”

• What do you have to do this week? Try to find 3 things that you need to do that are different from your partner! (You can use “have to” or “must.”)• “This week, I have to …”• “This week, my partner has to …”• “This week, my partner must …”

“Must” and “Have to” in Negative Statements• “Must” and “have to” have different meanings in negative

statements!

Think about the differences in each of these sets of sentences:

Parents must not spank their children.Parents don’t have to spank their children.

Children must not eat all the food.Children don’t have to eat all the food.

I must not tell my mom the secret.I don’t have to tell my mom the secret.

“Must” and “Have to” in Negative StatementsWhat is the difference?

• Must not: there is no choice; it is not allowed

• Don’t/doesn’t have to: it is not necessary (there is a choice)

Conjugation of “have to” vs. “must” in Negative Statements• Have to:

I don’t have to We don’t have toYou don’t have toShe doesn’t have to They don’t have to

• MustI must not We must notYou must notShe must not They must not

What are the differences between these verbs?

Practice with a partner ….• Make 3 rules that you think would be important for your child

(pretend you have children if you don’t have any!).

Begin your rules this way: My child must not _______.

Practice with a partner …• Now imagine that you are a child again and are describing

things you wish you didn’t have to do (things you wish weren’t necessary). Write 3 things that you wished you didn’t have to do as a child.

Begin your sentences this way: When I was a child, I wished I didn’t have to __________.

Practice: Choose a negative form of “must” or “have to”• Parents ___________ make rules about everything, but some things

are very dangerous for children. Parents should teach their children that they ___________ do these things. For example, children __________ always stay out of the kitchen, but they __________ touch a hot oven!

Practice: Use a negative form of “must” or “have to”• Parents don’t have to make rules about everything, but some things

are very dangerous for children. Parents should teach their children that they must not do these things. For example, children don’t have to always stay out of the kitchen, but they must not touch a hot oven!