1. (n.) The act of inserting anything between parts that are already established; as, the interpolation of likely causes\.

2. (n.) That which is introduced or inserted, especially something foreign or spurious.

3. (n.) The method or operation of finding from a few given terms of a series, as of numbers or observations, other intermediate terms in conformity with the law of the series.

addition affix allonge appendix approximation aside cadenza coda codicil commentary differentiation division embedment enclitic entrance envoi epilogue episode equation evolution extempore extrapolation flourish graft grafting hot lick impaction impactment implantation impromptu improvisation infix infixion infusion injection inoculation insert insertion insinuation integration intercalation interjection interlineation interlocution introduction intromission inversion involution lick marginalia multiplication notation note obiter dictum parenthesis penetration perfusion postscript practice prefix proclitic proportion reduction remark rider riff scholia side remark subtraction suffix tail tessellation tossing-in transformation transplant transplantation vamp