- Right: Men who are industrious will succeed. [The relative clause restricts the meaning; it is inseparably connected with the noun it modifies, and to omit it would change the thought of the main clause.]
- Right: Thomas Carlyle, who wrote forty volumes, was of peasant origin. [The relative clause is non-restrictive; it is not inseparably connected with the noun it modifies, and to omit it would not change the thought of the main clause. Thus: Thomas Carlyle was of peasant origin.]
- Right: Where is the house that Jack built? [Restrictive.]
- Right: I went to Jack's house, which is across the street. [Non-restrictive.]
- Wrong: Students, who are lazy, do not deserve to pass. [The sentence as it stands says that all students are lazy, and that none of them deserve to pass. Without the commas, the sentence would mean that such students as are lazy do not deserve to pass.]
- Right: Students who are lazy do not deserve to pass.
The rule stated above for clauses applies also to phrases.
- Right. She, hearing the voice, turned quickly. [Hearing the voice is non-restrictive. It does not identify she, and the thought of the main clause is complete without it.]
- Right: Books pertaining to aeronautics are in demand. [Pertaining to aeronautics is restrictive. It explains what books are referred to, and without it the meaning of the main thought is changed.]
- Right: Our country, made up as it is of democratic people, lacks the centralized power of a monarchy. [Non-restrictive.]
- Right: A country made up of democratic people must be lacking in centralized power. [Restrictive. Made up of democratic people explains country and is essential to the thought of the sentence.]
[e.] Slightly parenthetical elements are set off by commas:
Direct address or explanation:
- Write soon, Henry, and tell all the news.
- They intend, as you know, to build a great dam across the river.
- His father, they say, was frugal and industrious.
- I, on my part, however, am unalterably opposed to the expenditure.
- He was, according to such reports as have reached me, altogether in the right.
Mild interjections:
- Well, we shall see.
- Come now, let's talk it over.
- But alas, the cupboard was bare.
- The custom is, oh, very old.
Absolute phrases:
- This being admitted, I shall proceed to my other evidence.