Etimology
From Middle English certeynly; equivalent to certain + -ly.
adverb
certainly (comparative more certainly, superlative most certainly)
In a way which is certain; with certainty.
Without doubt, surely.
An emphatic affirmative answer; of course.
Examples
he verily thought he had young live frogs in his belly, qui vivebant ex alimento suo, that lived by his nourishment, and was so certainly persuaded of it, that for many years following he could not be rectified in his conceit.
The torque was "built up" in the special back axle and the car crawled tankwise but very certainly over the obstacles without a jar or hesitation.
The accident was certainly caused by human error.
That was certainly sweet of him.
You may certainly join us for dinner.
So this was my future home, I thought! Certainly it made a brave picture. I had seen similar ones fired-in on many a Heidelberg stein. Backed by towering hills, […] a sky of palest Gobelin flecked with fat, fleecy little clouds, it in truth looked a dear little city; the city of one's dreams.
WikiLeaks did not cause these uprisings but it certainly informed them. The dispatches revealed details of corruption and kleptocracy that many Tunisians suspected, but could not prove, and would cite as they took to the streets.
Would you like it with ice? Certainly, and with lemon please.
Related words
synonyms
(with certainty): absolutely, beyond doubt, indubitably, sure thing, undoubtedly, wis (obsolete), without a doubt
(without doubt): definitely, doubtlessly, in fact, indeed, indisputably, indubitably, no doubt, really, sure, surely, truly, undoubtedly, unquestionably, wis (obsolete), without a doubt
(emphatic affirmative): damn right, damn straight, fo shizzle, for sure, oh yeah, wye aye (dialect)
coordinate terms
maybe, possibly, arguably, questionably, probably, perhaps