The word(s) "sister" appears 20 time(s) in 11 verse(s) in Quran in Muhammad Pickthal translation.

(1) And unto you belongeth a half of that which your wives leave, if they have no child; but if they have a child then unto you the fourth of that which they leave, after any legacy they may have bequeathed, or debt (they may have contracted, hath been paid). And unto them belongeth the fourth of that which ye leave if ye have no child, but if ye have a child then the eighth of that which ye leave, after any legacy ye may have bequeathed, or debt (ye may have contracted, hath been paid). And if a man or a woman have a distant heir (having left neither parent nor child), and he (or she) have a brother or a sister (only on the mother's side) then to each of them twain (the brother and the sister) the sixth, and if they be more than two, then they shall be sharers in the third, after any legacy that may have been bequeathed or debt (contracted) not injuring (the heirs by willing away more than a third of the heritage) hath been paid. A commandment from Allah. Allah is Knower, Indulgent.

(2) Forbidden unto you are your mothers, and your daughters, and your sisters, and your father's sisters, and your mother's sisters, and your brother's daughters and your sister's daughters, and your foster-mothers, and your foster-sisters, and your mothers-in-law, and your step-daughters who are under your protection (born) of your women unto whom ye have gone in - but if ye have not gone in unto them, then it is no sin for you (to marry their daughters) - and the wives of your sons who (spring) from your own loins. And (it is forbidden unto you) that ye should have two sisters together, except what hath already happened (of that nature) in the past. Lo! Allah is ever Forgiving, Merciful.

(3) They ask thee for a pronouncement. Say: Allah hath pronounced for you concerning distant kindred. If a man die childless and he have a sister, hers is half the heritage, and he would have inherited from her had she died childless. And if there be two sisters, then theirs are two-thirds of the heritage, and if they be brethren, men and women, unto the male is the equivalent of the share of two females. Allah expoundeth unto you, so that ye err not. Allah is Knower of all things.

(4) He saith: Enter into the Fire among nations of the jinn and humankind who passed away before you. Every time a nation entereth, it curseth its sister (nation) till, when they have all been made to follow one another thither, the last of them saith unto the first of them: Our Lord! These led us astray, so give them double torment of the Fire. He saith: For each one there is double (torment), but ye know not.

(5) O sister of Aaron! Thy father was not a wicked man nor was thy mother a harlot.

(6) When thy sister went and said: Shall I show you one who will nurse him? and we restored thee to thy mother that her eyes might be refreshed and might not sorrow. And thou didst kill a man and We delivered thee from great distress, and tried thee with a heavy trial. And thou didst tarry years among the folk of Midian. Then camest thou (hither) by (My) providence, O Moses,

(7) And tell the believing women to lower their gaze and be modest, and to display of their adornment only that which is apparent, and to draw their veils over their bosoms, and not to reveal their adornment save to their own husbands or fathers or husbands' fathers, or their sons or their husbands' sons, or their brothers or their brothers' sons or sisters' sons, or their women, or their slaves, or male attendants who lack vigour, or children who know naught of women's nakedness. And let them not stamp their feet so as to reveal what they hide of their adornment. And turn unto Allah together, O believers, in order that ye may succeed.

(8) No blame is there upon the blind nor any blame upon the lame nor any blame upon the sick nor on yourselves if ye eat from your houses, or the houses of your fathers, or the houses of your mothers, or the houses of your brothers, or the houses of your sisters, or the houses of your fathers' brothers, or the houses of your fathers' sisters, or the houses of your mothers' brothers, or the houses of your mothers' sisters, or (from that) whereof ye hold the keys, or (from the house) of a friend. No sin shall it be for you whether ye eat together or apart. But when ye enter houses, salute one another with a greeting from Allah, blessed and sweet. Thus Allah maketh clear His revelations for you, that haply ye may understand.

(9) And she said unto his sister: Trace him. So she observed him from afar, and they perceived not.

(10) It is no sin for them (thy wives) to converse freely) with their fathers, or their sons, or their brothers, or their brothers' sons, or the sons of their sisters or of their own women, or their slaves. O women! Keep your duty to Allah. Lo! Allah is ever Witness over all things.