8. To set off a subordinate clause, especially one introduced by a descriptive relative. Thus,—
I am going to take a last dinner with a most agreeable family, who have been my only neighbors ever since I have lived at Weston.—Cowper.
Note. No comma is used before a restrictive relative. Thus,—
- I want to know many things which only you can tell me.
- Perhaps I am the only man in England who can boast of such good fortune.
9. To set off a phrase containing a nominative absolute. Thus,—
They had some difficulty in passing the ferry at the riverside, the ferryman being afraid of them.—Defoe.
10. To set off however, nevertheless, moreover, etc., and introductory phrases like in the first place, on the one hand, etc.
11. To set off a parenthetical expression. For this purpose commas, dashes, or marks of parenthesis may be used.
When the parenthetical matter is brief or closely related to the rest of the sentence, it is generally set off by commas. Thus,—
I exercised a piece of hypocrisy for which, I hope, you will hold me excused.—Thackeray.