Probably means most likely or in all likelihood. Probably is the adverb form of the adjective probable, meaning “very likely to occur or be true.” Probably is used when you think something will happen or turn out to be true, but you're not certain enough to say it definitely will.

Is probably an adjective or adverb?

Probably is an adverb, so it describes the manner in which a verb is performed.

What is the adjective of probable?

adjective. /ˈprɒbəbl/ /ˈprɑːbəbl/ ​likely to happen, to exist or to be true.