There are two great classes of sentences according to the general principles upon which they are founded. These are termed the loose and the periodic.
In the loose sentence the main idea is put first, and then follow several facts in connection with it. Defoe is an author particularly noted for this kind of sentence.He starts out with a leading declaration to which he adds several attendant connections. For instance in the opening of the story of Robinson Crusoe we read:"I was born in the year 1632 in the city of York, of a good family, though not of that country, my father being a foreigner of Bremen, who settled first at Hull? he got a good estate by merchandise, and leaving off his trade lived afterward at York, from whence he had married my mother, whose relations were named Robinson, a very good family in the country and from I was called Robinson Kreutznaer? but by the usual corruption of words in England, we are now called, nay, we call ourselves, and write our name Crusoe, and so my companions always called me."
In the periodic sentence the main idea comes last and is preceded by a series of relative introductions. This kind of sentence is often introduced by such words as that, if, since, because. The following is an example:
"That through his own folly and lack of circumspection he should have been reduced to such circumstances as to be forced to become a beggar on the streets, soliciting alms from those who had formerly been the recipients of his bounty, was a sore humiliation."
On account of its name many are liable to think the loose sentence an undesirable form in good composition, but this should not be taken for granted. In many cases it is preferable to the periodic form.
As a general rule in speaking, as opposed to writing, the loose form is to be preferred, inasmuch as when the periodic is employed in discourse the listeners are apt to forget the introductory clauses before the final issue is reached.