Grammar: Possibility, Probability, Necessity/Obligation

GRAMMAR

1. Expressing possibility and probability2. Expressing necessity/obligation

Teacher: Mario Molina

To express possibility (something that is POSSIBLE), we use three modals verbs: could, may, and might In our course, these three verbs have the same meaning; they are synonyms. Go to the next slide to see some examples.

expressing possibility

Examples for could, may, and might:

1. I am not hungry now, but I could/may/might eat something later. (affirmative form)
2. Sabrina is feeling a little sick today; she could/may/might not go to class. (negative form)

expressing possibility

• We don't use "to" after the verbs could, may, and might, so the verb has to be in base form.
• We use "not" after the verbs could, may, and might when the sentence is in negative form.

REMEMBER!

NOW, LET'S TALK ABOUT PROBABILITY! GO TO THE NEXT SLIDE!

To express probability (something that is LOGICAL), we use two modals verbs: must and can't These two verbs are used differently. You must always analyze the context. Go to the next slide to see some examples.

expressing pROBAbility

We use must in the affirmative and negative form to express situations which are logical (or not). Here are some examples:

1. A: Who is that man next to Lorena?

B: It must be her brother; they have the same eyes!2. A: Look, Miguel is carrying an enourmous box!B: Yes, it looks big, but it must not be very heavy.

expressing pROBAbility

We use can't in the negative form to express situations which are not logical. Here are some examples:

1. A: I saw a ghost last night, now I'm so scared!

B: Calm down! That can't be real! I think that was just your imagination!2. No! This sandwich can't cost $45.000! That is crazy!

expressing pROBAbility

• We don't use "to" after the verbs must and can't, so the verb has to be in base form.
• We use "not" after the verb must when the sentence is in negative form.
• In this course, we always use can't in the negative form to express probability.

REMEMBER!

NOW, LET'S TALK ABOUT OBLIGATION/NECESSITY! GO TO THE NEXT SLIDE!

expressing OBLIGATION/NECESSITY

To express obligation or necessity, we use two modals verbs: must and have to In our course, these two verbs have the same meaning in the affirmative form; they are synonyms. Go to the next slide to see some examples.

Examples for must and have to in the affirmative form:

1. I must/have to submit my project before midnight today. If I don't, I will get a zero!

2. Silvia must/has to* take her medicine at 7:00 p.m. every day. The doctor recommended this.*Remember you must conjugate the verb "have to" in the third person! (he, she, it = has to)

expressing OBLIGATION/NECESSITY

In the negative form, the verbs must and have to have opposite meanings:

• must not = obligation
• don't have to = optionality

Go to the next slide to see some examples.

IMPORTANT!

Examples for must not (obligation):

1. You must not drink and drive! This is illegal!
2. Children must not smoke. It's bad for their health!

Examples for don't have to (optionality):

1. We don't have to complete the activities today. We can finish them tomorrow.
2. Jerry doesn't have to* go to his office every day. Two days a week, he works from home.

*Remember you must use "doesn't have to" in the third person! (he, she, it = doesn't have to)

expressing OBLIGATION/NECESSITY

Now it's time for practice!

Remember, you must always analyze the context and choose the best verb for the sentence!

Good luck!