The word(s) "vain" appears 38 time(s) in 38 verse(s) in Quran in Abdullah Yusuf Ali translation.

(1) And they say: "None shall enter Paradise unless he be a Jew or a Christian." Those are their (vain) desires. Say: "Produce your proof if ye are truthful."

(2) Even if thou wert to bring to the people of the Book all the Signs (together), they would not follow Thy Qibla; nor art thou going to follow their Qibla; nor indeed will they follow each other's Qibla. If thou after the knowledge hath reached thee, Wert to follow their (vain) desires,-then wert thou Indeed (clearly) in the wrong.

(3) Serve Allah, and join not any partners with Him; and do good- to parents, kinsfolk, orphans, those in need, neighbours who are near, neighbours who are strangers, the companion by your side, the wayfarer (ye meet), and what your right hands possess: For Allah loveth not the arrogant, the vainglorious;-

(4) To thee We sent the Scripture in truth, confirming the scripture that came before it, and guarding it in safety: so judge between them by what Allah hath revealed, and follow not their vain desires, diverging from the Truth that hath come to thee. To each among you have we prescribed a law and an open way. If Allah had so willed, He would have made you a single people, but (His plan is) to test you in what He hath given you: so strive as in a race in all virtues. The goal of you all is to Allah; it is He that will show you the truth of the matters in which ye dispute;

(5) And this (He commands): Judge thou between them by what Allah hath revealed, and follow not their vain desires, but beware of them lest they beguile thee from any of that (teaching) which Allah hath sent down to thee. And if they turn away, be assured that for some of their crime it is Allah's purpose to punish them. And truly most men are rebellious.

(6) And those who believe will say: "Are these the men who swore their strongest oaths by Allah, that they were with you?" All that they do will be in vain, and they will fall into (nothing but) ruin.

(7) Say: "O people of the Book! exceed not in your religion the bounds (of what is proper), trespassing beyond the truth, nor follow the vain desires of people who went wrong in times gone by,- who misled many, and strayed (themselves) from the even way.

(8) When thou seest men engaged in vain discourse about Our signs, turn away from them unless they turn to a different theme. If Satan ever makes thee forget, then after recollection, sit not thou in the company of those who do wrong.

(9) Say: "Shall we indeed call on others besides Allah,- things that can do us neither good nor harm,- and turn on our heels after receiving guidance from Allah? - like one whom the evil ones have made into a fool, wandering bewildered through the earth, his friends calling, come to us', (vainly) guiding him to the path." Say: "Allah's guidance is the (only) guidance, and we have been directed to submit ourselves to the Lord of the worlds;-

(10) This is the guidance of Allah: He giveth that guidance to whom He pleaseth, of His worshippers. If they were to join other gods with Him, all that they did would be vain for them.