The word(s) "plain" appears 82 time(s) in 82 verse(s) in Quran in Muhammad Pickthal translation.

(11) Allah made a covenant of old with the Children of Israel and We raised among them twelve chieftains, and Allah said: Lo! I am with you. If ye establish worship and pay the poor-due, and believe in My messengers and support them, and lend unto Allah a kindly loan, surely I shall remit your sins, and surely I shall bring you into Gardens underneath which rivers flow. Whoso among you disbelieveth after this will go astray from a plain road.

(12) O People of the Scripture! Now hath Our messenger come unto you, expounding unto you much of that which ye used to hide in the Scripture, and forgiving much. now hath come unto you light from Allah and plain Scripture,

(13) O People of the Scripture! Now hath Our messenger come unto you to make things plain unto you after an interval (of cessation) of the messengers, lest ye should say: There came not unto us a messenger of cheer nor any warner. Now hath a messenger of cheer and a warner come unto you. Allah is Able to do all things.

(14) Shall I tell thee of a worse (case) than theirs for retribution with Allah? (Worse is the case of him) whom Allah hath cursed, him on whom His wrath hath fallen and of whose sort Allah hath turned some to apes and swine, and who serveth idols. Such are in worse plight and further astray from the plain road.

(15) Say: O People of the Scripture! Stress not in your religion other than the truth, and follow not the vain desires of folk who erred of old and led many astray, and erred from a plain road.

(16) Obey Allah and obey the messenger, and beware! But if ye turn away, then know that the duty of Our messenger is only plain conveyance (of the message).

(17) Shall I seek other than Allah for judge, when He it is Who hath revealed unto you (this) Scripture, fully explained? Those unto whom We gave the Scripture (aforetime) know that it is revealed from thy Lord in truth. So be not thou (O Muhammad) of the waverers.

(18) How should ye not eat of that over which the name of Allah hath been mentioned, when He hath explained unto you that which is forbidden unto you unless ye are compelled thereto. But lo! many are led astray by their own lusts through ignorance. Lo! thy Lord, He is Best Aware of the transgressors.

(19) The chieftains of his people said: Lo! we see thee surely in plain error.

(20) And remember how He made you viceroys after A'ad and gave you station in the earth. Ye choose castles in the plains and hew the mountains into dwellings. So remember (all) the bounties of Allah and do not evil, making mischief in the earth.