The word(s) "vain" appears 33 time(s) in 33 verse(s) in Quran in Mohsin Khan translation.

(11) And had We willed, We would surely have elevated him therewith but he clung to the earth and followed his own vain desire. So his parable is the parable of a dog: if you drive him away, he lolls his tongue out, or if you leave him alone, he (still) lolls his tongue out. Such is the parable of the people who reject Our Ayat (proofs, evidence, verses, lessons, signs, revelations, etc.). So relate the stories, perhaps they may reflect.

(12) It is not for the Mushrikun (polytheists, idolaters, pagans, disbelievers in the Oneness of Allah), to maintain the Mosques of Allah (i.e. to pray and worship Allah therein, to look after their cleanliness and their building,), while they witness against their ownselves of disbelief. The works of such are in vain and in Fire shall they abide.

(13) Like those before you: they were mightier than you in power, and more abundant in wealth and children. They had enjoyed their portion (awhile), so enjoy your portion (awhile) as those before you enjoyed their portion (awhile); and you indulged in play and pastime (and in telling lies against Allah and His Messenger Muhammad صلى الله عليه وسلم) as they indulged in play and pastime. Such are they whose deeds are in vain in this world and in the Hereafter. Such are they who are the losers.

(14) They are those for whom there is nothing in the Hereafter but Fire, and vain are the deeds they did therein. And of no effect is that which they used to do.

(15) For those who answered their Lord's Call [believed in the Oneness of Allah and followed His Messenger Muhammad صلى الله عليه و سلم i.e. Islamic Monotheism] is Al-Husna (i.e. Paradise). But those who answered not His Call (disbelieved in the Oneness of Allah and followed not His Messenger Muhammad صلى الله عليه و سلم), if they had all that is in the earth together with its like, they would offer it in order to save themselves (from the torment, but it will be in vain). For them there will be the terrible reckoning. Their dwelling-place will be Hell; and worst indeed is that place for rest.

(16) And thus have We sent it (the Qur'an) down to be a judgement of authority in Arabic. Were you (O Muhammad صلى الله عليه و سلم) to follow their (vain) desires after the knowledge which has come to you, then you will not have any Wali (protector) or Waq (defender) against Allah.

(17) "They are those who deny the Ayat (proofs, evidence, verses, lessons, signs, revelations, etc.) of their Lord and the Meeting with Him (in the Hereafter). So their works are in vain, and on the Day of Resurrection, We shall assign no weight for them.

(18) They shall not hear therein (in Paradise) any Laghw (dirty, false, evil vain talk), but only Salam (salutations of peace). And they will have therein their sustenance, morning and afternoon. [See (V.40:55)].

(19) And those who turn away from Al-Laghw (dirty, false, evil vain talk, falsehood, and all that Allah has forbidden).

(20) Have you (O Muhammad صلى الله عليه وسلم) seen him who has taken as his ilah (god) his own vain desire? Would you then be a Wakil (a disposer of his affairs or a watcher) over him?