TESOL/Belief

How do you say you believe something 80% in English?

English has several ways to express our subjective belief in an event. They include I think that or I doubt that. (For more information about expressing the objective chance of an event, such as It's likely that, see Probability in English.)

Part of Speech	0%	10%	30%	50%	80%	90%	100%
Verb	can't imagine can't believe can't accept	really doubt very much doubt	doubt	can imagine	think guess suppose expect suspect	really think	know believe
Adjective						almost certain	sure (I was sure. ~~It was sure.~~) convinced certain
Phrase							under the impression of the opinion

Usage

Under the impression

We use under the impression if someone believes something, but in reality, they were wrong.

I was under the impression that it would rain today. (It was sunny.)
She was under the impression that he was coming at 5 PM. (He came at 6 PM.)

Suspect

We use suspect when we believe something about 80%, but we do not have much or any evidence. Often it is used to talk about negative things.

I suspect you are lying. (I think so but I can't prove it.)
I suspect she is coming. (I think so but she has not called me yet.)
So far my boss doesn't suspect anything. (My boss doesn't think I did anything, and he or she doesn't have any evidence to believe so.)

Disagreeing

We can use words indicating belief under 50% to disagree.

Doubt

We use doubt to disagree.

Will they finish on time? - I doubt it. (They will be early or late.)
Bill Clinton was the best president ever. - I doubt it. (I disagree.)

I don't know, I'm not sure

We can use I don't know (about it/that), I'm not sure (about it/that), or similar expressions to politely disagree. The real meaning is "I know and I don't think so," not "I don't know."

When you eat at a restaurant in Japan, you should pay a tip. - I don't know about that. I think tips are considered insulting in Japan.
I'm going to go swimming after eating a big meal. - I'm not sure that's a good idea. You might get sick.
Do you think you will get the job? - I don't know about it. It was a week ago and they haven't called me back.

Ellipsis

Often "I doubt it" undergoes ellipsis and becomes "doubt it" which is a short response that means we disagree.

Are you going back home this year? - Doubt it. (I don't think so.)

The same thing happens with "I don't know" and "I'm not sure."

Has the meeting finished? - Dunno. Nobody is back yet.
Is it going to rain? - Not sure. There's not a cloud in the sky.

In the extreme, "I don't know" becomes "uh-uh-uh" where each "uh" only retains the intonation of its origin in the phrase "I don't know."

Mechanics

Usually we express belief in English using verbs. If we are talking about probability, we usually do not use verbs.