[The boy that broke his leg has fully recovered (restrictive).] Note the omission of the comma before that. [My eldest brother, who is now in England, will return by June (non-restrictive).] Note the inclosure of the clause in commas.  See Appendix 5, rule 10.

In the first sentence it is evident that the intent of the writer is to separate, in thought, the boy that broke his leg from all other boys.  Although the clause does indeed describe the boy’s condition, it does so for the purpose of limiting or restricting thought to one especial boy among many.  In the second sentence the especial person meant is indicated by the word eldest.  The clause, who is now in England, is put in for the sake of giving an additional bit of information.

+38.  Constructions of Relative Pronouns.+—­Relative pronouns may be used as subject, object, object of a preposition, subject of an infinitive, and possessive modifier.

The relative pronoun is regarded as agreeing in person with its antecedent.  Its verb, therefore, takes the person of the antecedent:  [I, who am your friend, will assist you].

The case of the relative is determined by its construction in the clause in which it is found:  [He whom the president appointed was fitted for the position].

+39.  Compound Relative Pronouns.+—­The compound relative pronouns are formed by adding ever and soever to the relative pronouns who, which, and what.  These have the constructions of the simple relatives, and the same rules hold about person and case:  [Give it to whoever wishes it.  Give it to whomever you see].

+40.  Interrogative Pronouns.+—­The pronouns who, which, and what are used to ask questions, and when so used, are called interrogative pronouns. Who refers to persons; what, to things; and which, to persons or things.  Like the relatives who has three case forms; which and what are uninflected.

The implied question in the sentence, I know whom you saw, is, Whom did you see?  The introductory whom is an interrogative pronoun, and the clause itself is called an indirect question.

The words which, what, and whose may also be used as modifiers of substantives, and when so used they are called interrogative adjectives:  ["What manner of man is this?” Whose child is this? Which book did you choose?].

+41.  Demonstrative Pronouns.+—­This and that, with their plurals these and those, are called demonstrative pronouns, because they point out individual persons or things.

+42.  Indefinite Pronouns.+—­Some pronouns, as each, either, some, any, many, such, etc., are indefinite in character.  Many indefinites may be used either as pronouns or adjectives.  Of the indefinites only two, one and other, are inflected.