Meanings of “Should”

• Duty/obligation (weak)
  • He should be at home. (implies a weak obligation or normative expectation — less forceful than must)
  • Suggestion: emphasize it’s a weaker form of obligation.
• Expectation/probability
  • He should be at home. (I expect him to be at home, based on information; it’s highly probable.)
  • That should do. (I expect that to be sufficient.)
• Conditional (inverted)
  • Should you come, bring your friend. (a more formal or hypothetical conditional statement, equivalent to “If you happen to come…” or “If you were to come…”)
• Suggestion/advice
  • You should meditate regularly. (a recommendation for what is advisable or beneficial.)
• Regret/criticism of past action (with perfect infinitive)
  • You should have told me. (You didn’t tell me, and it was the right thing to do, or it would have been better if you had.)
  • Meaning: expresses that a different, better action could/ought to have been taken in the past.
• Surprise/unlikelihood (formal/subjunctive-like)
  • It’s strange that he should say that. (expresses mild surprise or incredulity about a fact or possibility.)
  • I insisted that they should wait. (often used as an alternative to the base-form subjunctive after verbs like insist, demand, recommend, especially in British English, adding a nuance of mild obligation or expectation.)
  • Meaning: indicates something unexpected, surprising, or a slightly softened sense of necessity/recommendation in a formal context.
• Questioning justification/hypothetical consequence
  • Why should I care? (implies there’s no reason to care, or questions the logic/justification of an action.)
  • How should I know? (implies an inability to know, often rhetorically.)
  • Meaning: used in rhetorical questions to express defiance, lack of justification, or inability.