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

(21) And when they hear Al-Laghw (dirty, false, evil vain talk), they withdraw from it and say: "To us our deeds, and to you your deeds. Peace be to you. We seek not (the way of) the ignorant."

(22) Of those who split up their religion (i.e. who left the true Islamic Monotheism), and became sects, [i.e. they invented new things in the religion (Bid'ah ), and followed their vain desires], each sect rejoicing in that which is with it.

(23) And indeed it has been revealed to you (O Muhammad صلى الله عليه وسلم), as it was to those (Allah's Messengers) before you: "If you join others in worship with Allah, (then) surely (all) your deeds will be in vain, and you will certainly be among the losers."

(24) Then, when he brought them the Truth from Us, they said: "Kill the sons of those who believe with him and let their women live"; but the plots of disbelievers are nothing but in vain!

(25) They will say: "Did there not come to you, your Messengers with (clear) evidence (and signs)?" They will say: "Yes." They will reply: "Then call (as you like)! And the invocation of the disbelievers is nothing but in vain (as it will not be answered by Allah)!"

(26) Have you seen him who takes his own lust (vain desires) as his ilah (god)? And Allah knowing (him as such), left him astray, and sealed his hearing and his heart, and put a cover on his sight. Who then will guide him after Allah? Will you not then remember?

(27) Those who disbelieve (in the Oneness of Allah, and in the Message of Prophet Muhammad صلى الله عليه وسلم), and hinder (men) from the Path of Allah (Islamic Monotheism), He will render their deeds vain.

(28) But those who disbelieve (in the Oneness of Allah - Islamic Monotheism), for them is destruction, and (Allah) will make their deeds vain.

(29) O you who believe! Obey Allah, and obey the Messenger (Muhammad صلى الله عليه وسلم) and render not vain your deeds.

(30) There they shall pass from hand to hand a (wine) cup, free from any Laghw (dirty, false, evil vain talk between them), and free from sin (because it will be lawful for them to drink).