2. A substantive standing in the predicate, but describing or defining the subject, agrees with the subject in case and is called a predicate nominative.
A predicate nominative is also called a subject complement or an attribute.
- Lobsters are crustaceans.
- A good book is a faithful friend.
- Shakspere was a native of Stratford-on-Avon.
- Arnold proved a traitor.
- Adams was elected president.
The rule for the case of the predicate nominative is particularly important with respect to pronouns ([§ 119]).
| I am he. | Are you she? |
| It is I. | It was we who did it. |
The predicate nominative is commonest after the copula is (in its various forms). It will be further studied in connection with intransitive and passive verbs ([§§ 214], [252]).
3. A substantive used for the purpose of addressing a person directly, and not connected with any verb, is called a vocative.
A vocative is in the nominative case, and is often called a nominative by direct address or a vocative nominative.
- Come, Ruth, give me your hand.
- Turn to the right, madam.
- Herbert, it is your turn.
- Come with me, my child.
Note. A vocative word is sometimes said to be independent by direct address, because it stands by itself, unconnected with any verb. That a vocative is really in the nominative case may be seen in the use of the pronoun thou in this construction: as,—I will arrest thee, thou traitor (see [§ 115]).