The word(s) "certain" appears 144 time(s) in 135 verse(s) in Quran in Abdullah Yusuf Ali translation.

(101) "And ye shall certainly know the truth of it (all) after a while."

(102) Now, when trouble touches man, he cries to Us: But when We bestow a favour upon him as from Ourselves, he says, "This has been given to me because of a certain knowledge (I have)!" Nay, but this is but a trial, but most of them understand not!

(103) "Or (lest) it should say: 'If only Allah had guided me, I should certainly have been among the righteous!'-

(104) "Or (lest) it should say when it (actually) sees the penalty: 'If only I had another chance, I should certainly be among those who do good!'

(105) The Hour will certainly come: Therein is no doubt: Yet most men believe not.

(106) Behold, the messengers came to them, from before them and behind them, (preaching): "Serve none but Allah." They said, "If our Lord had so pleased, He would certainly have sent down angels (to preach). Now we reject your mission (altogether)."

(107) But We will certainly give the Unbelievers a taste of a severe Penalty, and We will requite them for the worst of their deeds.

(108) We certainly gave Moses the Book aforetime: but disputes arose therein. Had it not been for a Word that went forth before from thy Lord, (their differences) would have been settled between them: but they remained in suspicious disquieting doubt thereon.

(109) Nay! they say: "We found our fathers following a certain religion, and we do guide ourselves by their footsteps."

(110) Just in the same way, whenever We sent a Warner before thee to any people, the wealthy ones among them said: "We found our fathers following a certain religion, and we will certainly follow in their footsteps."