PROBABLY

probably, likely, in all likelihood, in all probability, belike

(adverb) with considerable certainty; without much doubt; “He is probably out of the country”; “in all likelihood we are headed for war”

credibly, believably, plausibly, probably

(adverb) easy to believe on the basis of available evidence; “he talked plausibly before the committee”; “he will probably win the election”

Source: WordNet® 3.1

Etymology

Adverb

probably (comparative more probably, superlative most probably)

In all likelihood.

Synonyms

• (in all likelihood): likely, perhaps, maybe, possibly, presumably, most likely, doubtless, in all probability, perchance, as likely as not, as like as not

Source: Wiktionary

Prob"a*bly, adv.

Definition: In a probable manner; in likelihood. Distinguish between what may possibly and what will probably be done. L'Estrange.

PROBABLE

Prob"a*ble, a. Etym: [L. probabilis, fr. probare to try, approve, prove: cf. F. probable. See Prove, and cf. Provable.]

1. Capable of being proved. [Obs.]

2. Having more evidence for than against; supported by evidence which inclines the mind to believe, but leaves some room for doubt; likely. That is accounted probable which has better arguments producible for it than can be brought against it. South. I do not say that the principles of religion are merely probable; I have before asserted them to be morally certain. Bp. Wilkins.

3. Rendering probable; supporting, or giving ground for, belief, but not demonstrating; as, probable evidence; probable presumption. Blackstone. Probable cause (Law), a reasonable ground of presumption that a charge is, or my be, well founded.

– Probable error (of an observation, or of the mean of a number), that within which, taken positively and negatively, there is an even chance that the real error shall lie. Thus, if 3" is the probable error in a given case, the chances that the real error is greater than 3" are equal to the chances that it is less. The probable error is computed from the observations made, and is used to express their degree of accuracy.

– The probable, that which is within the bounds of probability; that which is not unnatural or preternatural; -- opposed to the marvelous.

Source: Webster’s Unabridged Dictionary 1913 Edition