The semicolon is used to denote a degree of separation greater than that indicated by the comma, but less than that indicated by the colon. It prevents the repetition of the comma and keeps apart the more important members of the sentence. The semicolon is generally used in long sentences, but may sometimes be properly used in short ones.
Rules for the Use of the Semicolon
1. When the members of a compound sentence are complex or contain commas.
Franklin, like many others, was a printer; but, unlike the others, he was student, statesman, and publicist as well.
With ten per cent of this flour the bread acquired a slight flavor of rye; fifteen per cent gave it a dark color; a further addition made the baked crumb very hard.
The meeting was composed of representatives from the following districts: Newton, 4 delegates, 2 substitutes; Dorchester, 6 delegates, 3 substitutes; Quincy, 8 delegates, 4 substitutes; Brookline, 10 delegates, 5 substitutes.
2. When the members of a compound sentence contain statements distinct, but not sufficiently distinct to be thrown into separate sentences.
Sit thou a patient looker-on; Judge not the play before the play be done;
Her plot has many changes; every day
Speaks a new scene. The last act crowns the play.
3. When each of the members of a compound sentence makes a distinct statement and has some dependence on statements in the other member or members of the sentence.
Wisdom hath builded her house; she hath hewn out her seven pillars; she hath killed her beasts; she hath mingled her wine; she hath furnished her table.
Each member of this sentence is nearly complete. It is not quite a full and definite statement, but it is much more than a mere amplification such as we might get by leaving out she hath every time after the first. In the former case we should use periods. In the latter we should use commas.
4. A comma is ordinarily used between the clauses of a compound sentence that are connected by a simple conjunction, but a semicolon may be used between clauses connected by conjunctive adverbs. Compare the following examples:
The play was neither edifying nor interesting to him, and he decided to change his plans.
The play was neither edifying nor interesting to him; therefore he decided to change his plans.
5. To indicate the chapter references in scriptural citations.
Matt. i: 5, 7, 9; v: 1-10; xiv: 3, 8, 27.
The semicolon should always be put outside quotation marks unless it forms a part of the quotation itself.
"Take care of the cents and the dollars will take care of themselves"; a very wise old saying.
And that's it for the semicolon. Next, that innocent-looking, yet surprisingly tricksy piece of punctuation, the dash.