In spoken English, who is used as objective instead of whom; as, "Who did you see?" "Who did he speak to?"
To tell the case of interrogatives.
102. The interrogative who has a separate form for each case, consequently the case can be told by the form of the word; but the case of which and what must be determined exactly as in nouns,—by the use of the words.
For instance, in Sec. 99, which is nominative in the first sentence, since it is subject of the verb had; nominative in the second also, subject of doth love; objective in the last, being the direct object of the verb shall take.
Further treatment of who, which and what.
103. Who, which, and what are also relative pronouns; which and what are sometimes adjectives; what may be an adverb in some expressions.
They will be spoken of again in the proper places, especially in the treatment of indirect questions (Sec. 127).
RELATIVE PRONOUNS.
Function of the relative pronoun.
104. Relative pronouns differ from both personal and interrogative pronouns in referring to an antecedent, and also in having a conjunctive use. The advantage in using them is to unite short statements into longer sentences, and so to make smoother discourse. Thus we may say, "The last of all the Bards was he. These bards sang of Border chivalry." Or, it may be shortened into,—