3. Vocative words, that is, words used in direct address, are set off by commas. “Come, men, let’s go!” “Well, sir, how now?” It is curious that in the expressions “Yes, sir,” “No, sir,” in pronouncing which we do not pause before “sir,” we still place a comma here. Probably no rule of punctuation is more neglected than this of vocative words. Something like this usage is the placing of a comma after the expletive Now. Thus: “Now, I think that the case is a little different.”
4. (a) Words or phrases forming a series are separated by commas when conjunctions are omitted; and the comma is used between the last two members of the series, conjunction or no conjunction. Thus: “Burns, Barnes of Dorsetshire, and Riley are poets of the people.” If the last comma were omitted, we should seem not to be considering each man separately. Exceptions: “little old man,” “fine fat hen,” etc.
(b) A rapid series of independent propositions, very closely related in sense, may be punctuated by commas. Thus: “I came, I saw, I conquered.” This is the only structure in which an independent statement, not introduced by a conjunction, is ever pointed with the comma. If there is any doubt whether or not the series is rapid enough to admit commas, semicolons should be used instead.
5. Relative clauses not restrictive[10] are set off by commas. This is a rather important rule. If I say, “The moon, which, as everybody is aware, goes round the earth, is cold,” the which clause does not so restrict or define the word “moon” that it is necessary to our understanding what is meant by “the moon”; the relative clause can be picked out bodily, and the sentence will still be intelligible. “The moon is cold,” is clear enough to people who live on the earth. They understand that the earth’s moon is meant. But suppose I say, “The moon which goes round the earth is smaller than one of Jupiter’s moons”; now the relative clause identifies, restricts the word “moon”—tells what moon is meant. The clause forms an integral part of the subject. It is no longer the moon merely, a thing that everybody knows about; it is one particular moon: the-moon-which-goes-round-the-earth. Occasionally such a clause can be identified by that, for many writers save this relative for restrictive clauses.
Written Exercise.—Copy and punctuate the following sentences, all of which, except the first, are from Robert Louis Stevenson. Defend orally your pointing:—
1. There goes President Harper who is so much interested in everything that interests students.
2. Marquis I said if you take another step I fire upon you.
3. In the midst of these imagine that natural clumsy unintelligent and mirthful animal John.
4. The terms and spirit in which he spoke of his political beliefs were in our eyes suited to religious beliefs and vice versâ.