The word(s) "plain" appears 70 time(s) in 69 verse(s) in Quran in Abdullah Yusuf Ali translation.

(51) Had We sent this as a Qur'an (in the language) other than Arabic, they would have said: "Why are not its verses explained in detail? What! (a Book) not in Arabic and (a Messenger an Arab?" Say: "It is a Guide and a Healing to those who believe; and for those who believe not, there is a deafness in their ears, and it is blindness in their (eyes): They are (as it were) being called from a place far distant!"

(52) Then watch thou for the Day that the sky will bring forth a kind of smoke (or mist) plainly visible,

(53) How shall the message be (effectual) for them, seeing that a Messenger explaining things clearly has (already) come to them,-

(54) Know ye (all) that Allah giveth life to the earth after its death! already have We shown the Signs plainly to you, that ye may learn wisdom.

(55) Allah has indeed heard (and accepted) the statement of the woman who pleads with thee concerning her husband and carries her complaint (in prayer) to Allah: and Allah (always) hears the arguments between both sides among you: for Allah hears and sees (all things).

(56) Say: "As to the knowledge of the time, it is with Allah alone: I am (sent) only to warn plainly in public."

(57) And what will explain to thee what Hell-Fire is?

(58) Nay more, it is for Us to explain it (and make it clear):

(59) And what will explain to thee what is the Day of Sorting out?

(60) And what will explain to thee what the Day of Judgment is?