The Colon, or Member, is a chief constructive part, or greater division, of a Sentence.
The Semicolon, or Half-member, is a less constructive part, or subdivision of a Sentence or Member.
A Sentence or Member is again subdivided into Commas, or Segments; which are the least constructive parts of a Sentence, or Member, in this way of considering it; for the next subdivision would be the resolution of it into Phrases and Words.
The Grammarians have followed this division of the Rhetoricians, and have appropriated to each of these distinctions its mark, or Point; which takes its name from the part of the Sentence which it is employed to distinguish; as follows:
| The Period | } | is thus marked | { | . |
| The Colon | } | { | : | |
| The Semicolon | } | { | ; | |
| The Comma | } | { | , |
The proportional quantity or time of the Points with respect to one another is determined by the following general rule: The Period is a pause in quantity or duration double of the Colon; the Colon is double of the Semicolon; and the Semicolon is double of the Comma. So that they are in the same proportion to one another as the Semibrief, the Minim, the Crotchet, and the Quaver, in Music. The precise quantity or duration of each Pause or Note cannot be defined; for that varies with the Time; and both in Discourse and Music the same Composition may be rehearsed in a quicker or a slower Time: but in Music the proportion between the Notes remains ever the same; and in Discourse, if the Doctrine of Punctuation were exact, the proportion between the Pauses would be ever invariable.
The Points then being designed to express the Pauses, which depend on the different degrees of connexion between Sentences, and between their principal constructive parts; to understand the meaning of the Points, and to know how to apply them properly, we must consider the nature of a Sentence, as divided into its principal constructive parts; and the degrees of connexion between those parts, upon which such division of it depends.
To begin with the least of these principal constructive parts, the Comma. In order the more clearly to determine the proper application of the Point which marks it, we must distinguish between an Imperfect Phrase, a Simple Sentence, and a Compounded Sentence.
An Imperfect Phrase contains no assertion, or does not amount to a Proposition or Sentence.
A Simple Sentence has but one Subject and one finite Verb.