The word(s) "fourth" appears 5 time(s) in 4 verse(s) in Quran in Mohsin Khan translation.

(1) In that which your wives leave, your share is a half if they have no child; but if they leave a child, you get a fourth of that which they leave after payment of legacies that they may have bequeathed or debts. In that which you leave, their (your wives) share is a fourth if you leave no child; but if you leave a child, they get an eighth of that which you leave after payment of legacies that you may have bequeathed or debts. If the man or woman whose inheritance is in question has left neither ascendants nor descendants, but has left a brother or a sister, each one of the two gets a sixth; but if more than two, they share in a third, after payment of legacies he (or she) may have bequeathed or debts, so that no loss is caused (to anyone). This is a Commandment from Allah; and Allah is Ever All-Knowing, Most-Forbearing.

(2) But As-Saihah (torment - awful cry) overtook them in the early morning (of the fourth day of their promised punishment days).

(3) (Some) say they were three, the dog being the fourth among them; and (others) say they were five, the dog being the sixth, - guessing at the unseen; (yet others) say they were seven, and the dog being the eighth. Say (O Muhammad صلى الله عليه وسلم): "My Lord knows best their number; none knows them but a few." So debate not (about their number) except with the clear proof (which We have revealed to you). And consult not any of them (people of the Scripture - Jews and Christians) about (the affair of) the people of the Cave.

(4) Have you not seen that Allah knows whatsoever is in the heavens and whatsoever is on the earth? There is no Najwa (secret counsel) of three but He is their fourth (with His Knowledge, while He Himself is over the Throne, over the seventh heaven), nor of five but He is their sixth (with His Knowledge), nor of less than that or more but He is with them (with His Knowledge) wheresoever they may be. And afterwards on the Day of Resurrection He will inform them of what they did. Verily, Allah is the All-Knower of everything.