These days I have been encountered with people use both "most likely" and "mostly likely." Which one is correct? Grammatically I think both are correct but the grammar check tool on my computer also marked "mostly likely" as a grammar error, which is confusing to me.

1 Answer 1


"Most likely" and "Mostly likely" mean different things, though "most likely" is far more common. As far as I can remember, I have never heard "mostly likely" used outside of this question, and "most likely" is a very common phrase.

Most likely means that of all the possible choices, this one is the most probable. E.g. He is most likely the culprit [and it is less likely that he is not culprit].

Mostly likely would mean that most of some object is likely and some of it is unlikely. For example, if a scientist writes a paper that makes many very believable predictions and a few unbelievable ones, that paper could be described as mostly likely.

There's also one more important difference: in "most likely," the word 'likely' can be used as an adverb whereas in "mostly likely" it must be an adjective. "It is most likely red" is grammatically correct but "It is mostly likely red" is not. This is most likely why your grammar checker is making a fuss.


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