| Definition -
A sentence that is not grammatically complete until the final clause or phrase is stated.
The following monster periodic sentence is from Gogol's short story The Overcoat:
"Even at those hours when the gray Petersburg sky is completely overcast and the whole population of clerks have dined and eaten their fill, each as best he can, according to the salary he receives and his personal tastes; when they are all resting after the scratching of pens and bustle of the office, their own necessary work and other people's, and all the tasks that an overzealous man voluntarily sets himself even beyond what is necessary; when the clerks are hastening to devote what is left of their time to pleasure; some more enterprising are flying to the theater, others to the street to spend their leisure staring at women's hats, some to spend the evening paying compliments to some attractive girl, the star of a little official circle, while some—and this is the most frequent of all—go simply to a fellow clerk's apartment on the third or fourth story, two little rooms with a hall or a kitchen, with some pretensions to style, with a lamp or some such article that has cost many sacrifices of dinners and excursions—at the time when all the clerks are scattered about the apartments of their friends, playing a stormy game of whist, sipping tea out of glasses, eating cheap biscuits, sucking in smoke from long pipes, telling, as the cards are dealt, some scandal that has floated down from higher circles, a pleasure which the Russian do never by any possibility deny himself, or, when there is nothing better to talk about, repeating the everlasting anecdote of the commanding officer who was told that the tail had been cut off the horse on the Falconet monument—in short, even when everyone, was eagerly seeking entertainment, Akaky Akakievich did not indulge in any amusement."
Click here to listen to full audio rendition of the story.
1. In contrast to a loose sentence, which is a sentence in which the main independent (i.e. grammatically complete) clause is followed by additional modifying clauses or phrases.