certainly

From Middle English certeynly; equivalent to certain +‎ -ly.

• (General American) IPA^(key): /ˈsɝtn̩li/
• (Received Pronunciation) IPA^(key): /ˈsɜːtn̩li/

• Audio (US)

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certainly (comparative more certainly, superlative most certainly)

1. In a way which is certain; with certainty.
   • 1624, Democritus Junior [pseudonym; Robert Burton], The Anatomy of Melancholy: […], 2nd edition, Oxford, Oxfordshire: Printed by John Lichfield and James Short, for Henry Cripps, →OCLC:
     , I.iii.2.2:

     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.

   • 1923, A. A. Hill, Automobile Dealer and Repairer, page 30:

     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.

2. Without doubt, surely.

   The accident was certainly caused by human error.

   That was certainly sweet of him.

   You may certainly join us for dinner.

   • 1908, W[illiam] B[lair] M[orton] Ferguson, chapter IV, in Zollenstein, New York, N.Y.: D. Appleton & Company, →OCLC:

     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.

   • 2013 June 7, Gary Younge, “Hypocrisy lies at heart of Manning prosecution”, in The Guardian Weekly, volume 188, number 26, page 18:

     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.

3. An emphatic affirmative answer; of course.

   Would you like it with ice?  Certainly, and with lemon please.

• (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)

• maybe, possibly, arguably, questionably, probably, perhaps

• soitenly

• “certainly”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.
• “certainly”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.