Should is a modal verb used to talk about what is right, reasonable, or expected. It covers advice, opinions, expectations, and mild obligations — situations where something is a good idea but not strictly required.
Like all modal verbs, should has one form for every subject, takes the base verb without to, and does not change in the third person.
Form
| STRUCTURE | |
|---|---|
| Positive | subject + should + base verb |
| Negative | subject + should not (shouldn't) + base verb |
| Question | Should + subject + base verb? |
There is no -s form, no -ing form, and no did. Questions and negatives are formed directly with should — no auxiliary do is needed.
Advice and recommendations
The most common use. When you tell someone what you think is the right or sensible thing to do, should is the natural choice.
The negative gives advice against something.
Questions with should ask for guidance or a recommendation.
Opinions
Should also expresses what the speaker thinks is right or appropriate, even when no one is asking for advice. This often appears with phrases like I think, I believe, or in my opinion.
The line between advice and opinion is thin. The difference is context: advice is directed at someone making a decision; an opinion is a general judgment about what would be right.
Expectation
When something is likely based on logic or available information, should signals that you expect it to happen — but you are not completely certain.
This meaning is close to will probably. If you say the meeting should finish by noon, you expect it to but acknowledge it might not.
Mild obligation
Should can express a duty or rule that is important but not as strong or urgent as must. Think of it as something that is expected of you rather than something absolutely required.
The difference from must is strength. You must wear a seatbelt presents it as a strict rule; you should wear a seatbelt presents it as a strong recommendation. Stronger obligation is covered separately.
Should have + past participle
Should have + past participle looks back at the past and says that something was the right thing to do — but it didn't happen. It expresses regret, criticism, or a missed opportunity.
The negative — shouldn't have — means that something happened, and it was a mistake.
In both cases, the reality was the opposite of what should describes. I should have called means I didn't call. He shouldn't have left means he did leave.
This structure gives only a brief introduction here. Full modal perfect forms are covered separately.
Ought to
Ought to means the same as should and works in all four meanings — advice, opinion, expectation, mild obligation. It is slightly more formal and far less common in everyday speech.
In negatives and questions, should is almost always preferred over ought to. Forms like ought we to...? or he oughtn't to... are grammatically correct but sound old-fashioned to most speakers.
Common mistakes
Adding to after should
Using do/does/did in questions and negatives
Third-person -s
Wrong form after should
Should have (past regret)