The act of foisting a word or passage into a manuscript or book.

A spurious word or passage inserted in the genuine writings of an author. I have changed the situation of some of the Latin verses, and made some interpolations.

In mathematics, that branch of analysis, which treats of the methods by which, when a series of quantities succeeding each other, and formed all according to some determinate law, are given, others subject to the same law may be interposed between them.