5. The Comma
47. Parenthetic Expressions.—Parenthetic words, phrases, and clauses, whether used at the beginning, middle, or end of a sentence, are set off by commas when they cause a marked interruption between grammatically connected parts of the sentence. If in doubt about the need of a comma, omit it.
Right.—He, like many others, believes firmly in the rightness of the new movement.
48. Words in Apposition.—A word in apposition with another word and meaning the same thing should be set off by commas.
Right.—Henry Owen, lineman for the local telegraph company, was the only witness of the accident.
49. With "namely," "that is," etc.—A comma is placed before and, namely, viz., that is, i.e., as, to wit, etc., when introducing an example, an illustration, or an explanation.
50. Contrasted Words and Phrases.—Set off contrasted words and phrases with commas.
Right.—Hard work, not genius, was what enabled him to succeed.
Right.—The faster they work, the better they are paid.
51. Introductory Words and Phrases.—Introductory words, phrases, and clauses at the beginning of a sentence, when they modify the whole sentence and serve as a connective, are set off by commas.