Department of DoubtForm 13: The rare yes

"I think so": what it means, and 30 other ways to say it

"I think so" is a yes with a seatbelt on. It agrees, but it leaves room for being wrong. Here is how sure it really is, how it compares with "I believe so" and "I guess so", and 30 other ways to say yes, from very careful to completely certain.

The short answer

"I think so" means "I believe the answer is yes." It is an opinion, not a guarantee. Said in answer to a question ("Is the shop open today?" "I think so."), it tells the listener: probably yes, but check if it matters.

How sure is "I think so"?

There is no exact number, but most people hear it as fairly likely, not certain. Tone moves it up or down:

"I think so." Level voice: a reasonable yes.
"I think so..." Stress on think, trailing off: real doubt. The speaker is far from sure.
"Yes, I think so." Leading with yes: confident, just polite about it.
"I think so?" Rising tone, or a question mark in text: the speaker is asking you to confirm.

Why the "so"?

"So" stands in for the whole idea that was just mentioned. Instead of repeating "I think the shop is open today", English shortens it to "I think so." The same pattern appears in "I hope so", "I'm afraid so" and "I guess so". The negative version moves the "not" to the verb of thinking, which gives "I don't think so". The full story of that is in what "I don't think so" means.

"I think so", "I believe so", "I guess so"

I think so: everyday, a likely yes.
I believe so: the same meaning, a bit more formal. Common at work and in customer service.
I guess so: often reluctant agreement rather than belief. "Can we leave early?" "I guess so."
I suppose so: similar to "I guess so", sometimes with a sigh.
I hope so: you want it to be yes, but you have no real evidence.

30 other ways to say "I think so"

Careful (probably yes)

I believe so.
As far as I know, yes.
Probably.
I'd say so.
Most likely.
That's my understanding.
I'm fairly sure.
Last I heard, yes.

At work

I believe that's correct.
That matches what I have.
Yes, though I'll double-check.
That should be right.
To the best of my knowledge, yes.
I expect so.
Yes, unless something has changed.

Casual

Yeah, I think so.
Pretty sure.
Should be.
I reckon so.
Seems like it.
I'd guess yes.
Sounds right.

Confident (definitely yes)

Yes.
Definitely.
Absolutely.
I'm sure.
Without a doubt.
No question.
Fine. I think so. (The Department's rare, reluctant approval.)
Stamped and approved.

The Department's rare yes

The Department of Doubt says "I don't think so" to the internet almost every day. About once every few weeks a claim turns out to be simply true, and it gets a green stamp: FINE. I THINK SO. Dogs in tiny raincoats got one. Browse the archive to find the others, see today's case, or give your own claim the green stamp in Stamp Anything.

Questions about "I think so"

What does "I think so" mean?

It means "I believe the answer is yes, but I am not completely sure." It is a careful yes that leaves a little room for being wrong.

Is "I think so" a yes?

Mostly. The listener should treat it as a likely yes, not a promise. If you need certainty, a follow-up such as "Can you confirm?" is fair.

What is the difference between "I think so" and "I believe so"?

They mean the same. "I believe so" sounds a little more formal and is common at work and in customer service. "I think so" is the everyday version.

Is "I guess so" the same as "I think so"?

Not quite. "I guess so" often means reluctant agreement ("Can we leave early?" "I guess so."), while "I think so" is about what you believe is true.

What is the opposite of "I think so"?

"I don't think so." It is the careful no, and it can also be a firm refusal depending on tone. See the full guide to what "I don't think so" means.

The Department of Doubt is satire, but this page is a plain guide to an English phrase. See the satire notice. Looking for the other half? Read 30 ways to say "I don't know".