Should vs. Supposed To

'Should' and 'supposed to' may confuse learners as they are used to talk about duty. In this lesson, we will learn their differences, similarities, and uses.

What Is Their Main Difference?

The main difference between 'should' and 'supposed to' is that 'should' is a modal verb while 'supposed to' is a modal verb phrase.

'Should' is a modal verb. Modal verbs give additional information about the main verb. We use it to talk about possibilities, make suggestions, give advice, predict the future, etc. 'Should' is the past tense of the modal verb 'shall.' For instance:

Jordan should be home by now.

They should take down their Halloween decorations, it's almost December.

'Supposed to' is a phrase that has a similar function to modal verbs. That is why it is called 'modal verb phrase.' 'Supposed to' is used to talk about duty, and intended events and actions. For instance:

You were supposed to give a speech about your paper.

She is supposed to be studying right now.

Similarities

Talking about Duty

We use 'should' and 'supposed to' to talk about obligations and duties. Duties and obligations are actions that are legally and morally required to be fulfilled. 'Should' represents a weaker obligation. For instance:

I should be home before midnight.

I am supposed to be home before midnight.

Talking about Intended Actions

We use 'should' and 'supposed to' to talk about actions or events that we expect them to happen. These events have been preplanned and programmed. For instance:

The battery should last longer than 3 months.

The battery is supposed to last longer 3 months.

Differences

Advice

We use 'should' to ask for or give advice. When we are giving advice, we are expressing what we thing is the right thing to do. When we are asking for advice, we are asking for the right ways to do something. Have a look:

What should I do?

Here, we are asking for advice.

You should try therapy.

Here, we are giving advice.

Negation

'Should' and 'supposed to' can create negative sentences:

Should

To create negative sentences with 'should,' we simply add 'not' after 'should' as illustrated below:

Should → Should not → Shouldn't

Here are some examples for clarification:

I should face him. → I shouldn't face him.

He should take the trash out. → He shouldn't take the trash out.

Supposed to

To make a sentence that contains 'supposed to' negative, we follow the pattern shown below:

Subject + be + not + supposed + to + main verb + …?

Watch:

I was supposed to get off the bus. → I was not supposed to get off the bus.

I was supposed to meet him yesterday. → I wasn't supposed to meet him yesterday.

Question

'Should' and 'supposed to' can create interrogative sentences:

Should

To create questions, we invert 'should' as illustrated in the examples below:

I should talk her out of it. → Should I talk her out of it?

He should report them to the office. → Should he report them to the office?

Supposed to

Creating questions with 'supposed to' is a little tricky. Unlike modal verbs, we do not change the position of 'supposed to.' We invert the 'to be' verb as shown in the pattern below:

Be + subject + supposed + to + main verb + …?

For example:

I was supposed to call you. → Was I supposed to call you?

She is supposed to give him a lift. → Is she supposed to give him a lift?

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