1. It is used after a word or group of words to express command, surprise, or emotion.
2. Enclosed in brackets, it is used in a quotation to express surprise, irony, or contempt.
101. Wake up! Something is going wrong!
102. Oh, how hard my lot[!]
The practice of using two or three exclamation-points together is not now followed.
ELLIPSIS
When one, for the sake of brevity or otherwise, omits a word, a group of words, or one or more sentences from a quotation, such omission, or ellipsis, is indicated by either periods or stars. Periods are generally preferred on the ground that they look better on the printed page than stars. Unfortunately, the number of periods used for an ellipsis is not definitely fixed by convention. Some writers and printers use three, and others use four; we prefer three.
If words are omitted from the end of a sentence, the end-mark of the sentence, if an exclamation-point or an interrogation-point, is retained, and follows the three periods. If the end-mark of the sentence is a period, and one or more sentences following are omitted, there will be four periods at this point. There will be the same number if words are omitted from the beginning of a sentence following a sentence ending with a period.
If stars are used, the closing period is retained.