a suffix, occurring in adjectives of Greek and Latin origin, meaning “pertaining to,” and (in nouns thence derived) also imitated in English (coffin; cousin, etc.).
Origin of -in1
Middle English -in, -ine < Old French < Latin -inus, -ina, -inum < Greek -inos, -inē, -inon
Definition for -in (2 of 3)
a noun suffix used in a special manner in chemical and mineralogical nomenclature (glycerin; acetin, etc.). In spelling, usage wavers between -in and -ine. In chemistry a certain distinction of use is attempted, basic substances having the termination -ine rather than -in (aconitine; aniline, etc.), and -in being restricted to certain neutral compounds, glycerides, glucosides, and proteids (albumin; palmitin, etc.), but this distinction is not always observed.
Origin of -in2
< New Latin -ina. See -ine2
Definition for -in (3 of 3)
a suffixal use of the adverb in, extracted from sit-in, forming compound nouns, usually from verbs, referring to organized protests through or in support of the named activity (kneel-in; chain-in; be-in) or, more generally, to any organized social or cultural activity (cook-in; sing-in).
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for -in
suffix forming nouns
indicating a neutral organic compound, including proteins, glucosides, and glyceridesinsulin; digitoxin; tripalmitin
indicating an enzyme in certain nonsystematic namespepsin
indicating a pharmaceutical substancepenicillin; riboflavin; aspirin
indicating a chemical substance in certain nonsystematic namescoumarin
Word Origin for -in
from New Latin -ina; compare -ine ²
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Medicine definitions for -in
Neutral chemical compound:inulin.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.