1. Obligation or Expectation:
* This is the most common use. "Supposed to" indicates something is expected or required, often by a rule, agreement, or social norm.
* Example: "You're supposed to wear a uniform to work." (This is a rule or expectation of the job).
2. Belief or Assumption:
* "Supposed to" can express a belief or assumption, even if it's not necessarily true.
* Example: "He's supposed to be a great musician, but I've never heard him play." (There is a belief or assumption, but it might not be accurate).
3. Past Expectation or Plan:
* "Supposed to" can refer to something that was planned or intended in the past, even if it didn't happen.
* Example: "We were supposed to go on vacation last month, but we had to cancel." (The plan existed, but it was changed).
4. Contrasting with Reality:
* "Supposed to" can highlight a contrast between what was expected and what actually happened.
* Example: "The meeting was supposed to start at 10:00, but we ended up starting at 10:30."
Here are some things to keep in mind:
* Formal vs. Informal: "Supposed to" is more common in informal language. In formal writing, you might use "expected to" or "required to" instead.
* Tense: The verb after "supposed to" is usually in the infinitive form (e.g., "to be," "to do").
* Negative: The negative form is "not supposed to."
Examples:
* Obligation: "I'm supposed to be at the library by 5pm."
* Belief: "She's supposed to be a genius."
* Past Plan: "We were supposed to go to the beach yesterday."
* Contrast: "The train was supposed to arrive at 8:00, but it's now 8:30."
To summarize: Use "supposed to" when you want to convey obligation, expectation, belief, a past plan, or a contrast between what was expected and reality.