Definition of who:

• One; any; one.
• An interrogative; as, who spoke? a relative, used of persons; a compound relatiye, meaning the person or persons that; as, who crosses this line will suffer.
• Both rel. and interrog., always for persons: what person? which person.
• Which or what person.
• Originally, an interrogative pronoun, later, a relative pronoun also; -- used always substantively, and either as singular or plural. See the Note under What, pron., 1. As interrogative pronouns, who and whom ask the question: What or which person or persons? Who and whom, as relative pronouns ( in the sense of that), are properly used of persons ( corresponding to which, as applied to things), but are sometimes, less properly and now rarely, used of animals, plants, etc. Who and whom, as compound relatives, are also used especially of persons, meaning the person that; the persons that; the one that; whosoever.
• A specialized agency of the United Nations designed as a coordinating authority on international health work; its aim is to promote the attainment of the highest possible level of health by all peoples.
• A relative pron. always referring to persons, and much used in asking questions.
• That.
• He, she, or they that.
• A word which refers to a person; which of many, as, " who is the person who has a right to exercise it?" used interrogatively.

Usage examples for who

1. But, first of all, who were they?"  Aurora the Magnificent by Gertrude Hall

2. " Who else would have seen it?  Bohemians of the Latin Quarter by Henry Murger

3. Who could say anything of her?  A Country Gentleman and his Family by Mrs. (Margaret) Oliphant

4. Who else will he do it to?  Entire PG Edition of The Works of William Dean Howells by William Dean Howells