PERIOD, in grammar, denotes a small compass of discourse, containing a perfect sentence, and distinguished at the end by a point, or full stop, thus (.); and in members or divisions marked by commas, colons, &c.
Father Buffier observes two difficulties in the use of the period, or point; i. e. in distinguishing it from the colon, or double point; and in determining justly the end of a period, or perfect sentence. It is remarked, that the supernumerary members of a period, separated from the rest by colons and semicolons, usually commence with a conjunction: yet it is true these same conjunctions sometimes rather begin new periods than supernumerary members of old ones. It is the sense of things, and the author's own discretion, that must make the proper distinction which of the two in effect it is. No rules will be of any service, unless this be admitted as one, that when what follows the conjunction is of as much extent as what precedes it, it is usually a new period; otherwise not.
The second difficulty arises hence, that the sense appears perfect in several short detached phrases, where-in it does not seem there should be periods; a thing frequent in free discourse: as, We are all in suspense: make your proposals immediately: you will be to blame for detaining us longer. Where it is evident, that simple phrases have perfect senses like periods, and ought to be marked accordingly; but that the shortness of the discourse making them easily comprehended, the pointing is neglected.
De Colonia defines period a short but perfect sentence, consisting of certain parts or members, depending one on another, and connected together by some common vinculum. The celebrated definition of Aristotle is, a period is a discourse which has a beginning, a middle, and an end, all visible at one view. Rhetoricians consider period, which treats of the structure of sentences, as one of the four parts of composition. The periods allowed in oratory are three: A period of two members, called by the Greeks diolos, and by the Latins bimembriis; a period of three members, tricoloris, trimembriis; and a period of four, quadrimembriis, tetracoloris. See PUNCTUATION.