-in

A suffix widely used to form names of biochemical substances, including proteins (e.g., globulin), lipids (lecithin), hormones (insulin), botanical principles (digoxin), antibiotics (streptomycin), synthetic drugs (aspirin), dyes (eosin), and others; initially a variant of -ine; in a few terms (e.g., dentin, thyroxin, spellings with and without final e are both found. [G. -inos,, L. -inus, adj. suffixes]