My intermediate ESL students enjoy beginning each class with a dictation as a way to review previously learned vocabulary items. Recently, the dictation included the expression “be supposed to.” A couple of students raised their hands and asked me to spell and explain it. I was rather surprised that they were unfamiliar with such a common phrase.

I talked to the instructors in my program who teach the lower levels and found that they did not cover “be supposed to” in their classes. I also had a hard time finding it in grammar textbooks. Since this expression is used so frequently in conversational English, I felt that it was time for a post explaining its usage and providing practical tips on how to use it correctly.

Understanding the basics

"Be supposed to" is an idiomatic expression used for obligation, expectation, or intention. Found mainly in the simple present and simple past tenses, it is typically used to express what is considered normal, customary, or required in a given situation. While its primary function is to indicate duty or responsibility, "be supposed to" can also convey assumptions or beliefs about what is likely or intended to happen.

Structure

The structure of this phrase is straightforward:

subject + Be verb + supposed to + base form of the main verb

Usage in the simple present

1. Expressing obligation

• Example: I am supposed to submit my report tomorrow morning.
• Explanation: In this context, "am supposed to" indicates a sense of obligation or responsibility. The speaker is following their boss's request.
• Note: "Must" could also be used in this example, but it would suggest more serious consequences if the speaker fails to meet the dealine. In other words, if "must" is used, the speaker could be fired if they don't submit their report on time. With "am supposed to," the speaker may face lesser consequences such as being reprimanded.

2. Indicating expectation

• Example: It is supposed to rain tomorrow.
• Explanation: Here, "is supposed to" conveys an expected occurrence. Perhaps the speaker has read a weather report or watched the news to get this information and believes that it is true or probable.

3. Describing intention

• Example: My aunt and uncle are supposed to visit us this summer. 
• Explanation: In this case, "are supposed to" suggests an intended action. The speaker's aunt and uncle have plans to visit.

4. Repeating hearsay

• Example: The Yellow Umbrella Cafe is supposed to have the best pizza in town.
• Explantion: The speaker has heard other people talk about the Yellow Umbrella Cafe, or they may have read about it online, in a newspaper, or in a magazine. 

Usage in the simple past

When discussing the past, the phrase "was/were supposed to" is used to express unfulfilled expectations or unmet obligations.

• Example: She was supposed to call me when she reached her destination, but she forgot.
• Explanation: In this instance, "was supposed to" indicates an obligation that was not met in the past. The result could lead to disappointment, anger, or surprise.

Common pitfalls to avoid

1. Don't confuse "be supposed to" with the verb "suppose" or the adverb "supposedly." 
2. Pay attention to the correct conjugation of the verb "to be" based on the subject of the sentence.

Do your learners incorporate "be supposed to" in their speech and writing? How do you present "be supposed to" in your classes? We'd love to hear your thoughts and ideas.