MODAL VERBS OF POSSIBLITY AND OBLIGATION

Modal verbs - UNIT 3

Let's check them out

PRESENT

PAST

Possibility

Past possibility or ability

Can/can't

Could/ couldn't Was/were able to Wasn't/weren't able to

Obligation/no obligation

Must Have to Don't have to

Obligation / no obligation in the past

Prohibition

Mustn't

Had to Didn't have tp

MODALS OF POSSIBILITY

IN THE PRESENT

• Can

wE use 'can' to talk about possibilities in relation to general topics and things we know (S + CAN + INFINITIVE) "That dog can be dangerous" Fast food can increase health issues"

• Can't

We use 'can't' to talk about impossibility (S + CAN'T + INFINITIVE) "Your body can't make energy without B vitamins" "This sausage dog can't be so cute"

MUST

things you are obligated to do

• You MUST drink 1.5 L of water each day at least
• Teenagers must exercise 3 days a week to be healthy

S + MUST + INFINITIVE (play, eat, do...)

HAVE TO

things you need to do

• I have to practise sport 2 times a week to stay fit
• She has to eat two breakfast to have energy in the mornings

S + HAVE/HAS TO + INFINITIVE (play, eat, do...)

DON'T HAVE TO

things you DON'T NEED TO DO

• You don't have to train football this afternoon
• He doesn't have to change his diet, it's okay.

S + DON'T HAVE / DOESN'T HAVE TO + INF.

MUSTN'T

MODALS OF PROHIBITION

"I can do it"

"he can't do it"

wE USE IT WHEN SOMETHING IS FORBIDDEN TO DO

• You musn't eat fast food every weekend
• He mustn't jump off the bridge
• They mustn't eat more than 50gr of chocolate each day, they have diabetes

LET'S PRACTISE THIS!

TALKING ABOUT PAST ABILITY AND POSSIBILITY

s + could + verb (INF.) / s + couldn't + V (inf.)

• In the past, I could focus better on studying
• We couldn't buy vegan products 50 years ago
• They couldn't keep fit as easily before as now

s + was/were able to + verb (INF.)s + wasn't / weren't able to + Verb (inf.)

• In the past, I was able to study more hours
• People were able to do better in memory test

• They weren't able to go to the gym as we do

info

LACK OF OBLIGATION IN THE PAST

OBLIGATION IN THE PAST

S + HAD TO + V (inf)

S+ DIDN'T HAVE TO + V (inf)

We DON'T use "MUST" for the Past.

Just the negative form

• We didn't have to buy more food for the party
• You didn't have to eat all those calories for training

• We had to finish the project by Friday
• I had to rest before going to the match

BASIC CONCEPTS

• They are followed by an infinitive

(Fast food can produce health problems)

• They don't use third person -s; except in the case of "have to/don't have to"
• The don't need auxiliars; except "don't have to"

(They mustn't eat more calories; they don't have to practise more sports)