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.
Macaulay. [
1913 Webster]