“Suppose To” and “Supposed To” look very similar. It’s one of those situations in which some people just assume that, consequently, they should mean the same and have the same use.
Is it true, though? Can we use “Suppose To” and “Supposed To” interchangeably, to convey the same meaning?
“Supposed To” is the correct form and means the subject is expected to do (or not to do) something, or be somewhere. It’s related to what a person should do and expectations. “Suppose To” is incorrect, because “Suppose” usually appears by itself. It means to make an assumption about something.
Let’s look at some examples:
- She was supposed to take out the trash.
- She was suppose to take out the trash (incorrect)
- I suppose you know what you’re doing.
- I supposed you know what you’re doing. (incorrect)
- I suppose to know what you’re doing. (incorrect)
The first set of sentences show the correct use of “Supposed To”. Someone was expected to take the trash out. “Suppose To”, in that context, obviously fails to work.
In the second set, we have a correct example of “Suppose” – where it appears by itself, indicating one’s assumption about another individual.
It also contains 2 incorrect examples. One, including “Supposed”, and another, including “Suppose To”. Try reading the incorrect sentences out loud, and you’ll notice they’re even sound off.
“Suppose To” is grammatically incorrect. “Suppose” by itself, on the other hand, is correct, and you can use it if it makes sense in your speech. “Suppose” something means you’re making an assumption about that subject. It indicates you’re not completely sure, but have reason to believe that fact.
Take a look at the examples below:
- George was suppose to be at home resting. (incorrect)
- I wasn’t suppose to be at that party last night. (incorrect)
- She isn’t suppose to know that. (incorrect)
- I suppose that your answer could be the correct one.
- She doesn’t suppose to know the answer.
- Claude doesn’t know much about food, I suppose.
The first three sentences are wrong and show us how not to use “Suppose To”.
The last three, sentences 4 to 6, show correct ways of telling someone you are (or aren’t) making an assumption. In the first one, for example, I assume the answer is correct, In other words, I have reason to believe that it was the correct answer (it’s an assumption).
“Supposed To” is an expression we use to indicate someone should or shouldn’t do something. It’s connected to the idea of doing (or sometimes, not doing) the right thing, and what is expected of us in certain situations.
This is how to use “Supposed To” in a sentence:
- He was supposed to meet me at the restaurant.
- I don’t know where Daisy is, but she is supposed to be at work right now.
- Danny was supposed to do his homework tonight.
- Will wasn’t supposed to be home after dark.
- I’m supposed to be at school tomorrow at 8am.
Every sentence in the example indicates what a person should or shouldn’t do, making it clear what are the expectations. Daisy, for example, should be at work (but is likely not).
Which of the forms we’re looking at is used more often? The graph from Google Ngram Viewer below will show us.
“Suppose To” appears at the bottom of the graph, as it would be expected for an expression that’s grammatically wrong and should be avoided.
“Supposed” is at the top by itself, followed by “Suppose”. “Supposed To” is right behind these two forms.
We wonder if “Supposed” by itself and “Supposed To” should be sort of counted together, consolidating a top appearance on the graph. Still, it’s a very interesting graph to look at and try to come up with some hypotheses about the use of those words.
“Supposed To”, as an indication of what someone should do, is a grammatically correct form that you can use. “Suppose To” is incorrect and should be avoided. If you wish to affirm what your assumptions are, you can use “Suppose” by itself, and it’d work out fine.
Martin is the founder of Grammarhow.com. With top grades in English and teaching experience at university level, he is on a mission to share all of his knowledge about the English language. Having written thousands of articles, he is an expert at explaining difficult topics in a simple language.
Connect with Martin on LinkedIn.