(a.) A interrogative pronoun, used both substantively and adjectively, and in direct and indirect questions, to ask for, or refer to, an individual person or thing among several of a class; as, which man is it? which woman was it? which is the house? he asked which route he should take; which is best, to live or to die? See the Note under What, pron., 1.
(pron.) A relative pronoun, used esp. in referring to an antecedent noun or clause, but sometimes with reference to what is specified or implied in a sentence, or to a following noun or clause (generally involving a reference, however, to something which has preceded). It is used in all numbers and genders, and was formerly used of persons.
(pron.) A compound relative or indefinite pronoun, standing for any one which, whichever, that which, those which, the . . . which, and the like; as, take which you will.
Example Sentences:
Who
Definition:
(object.) 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.