-mer

Also ‑mere, ‑meric, and ‑merous.

Part or segment.

Greek meros, part.

Terms in ‑mer often denote substances whose molecules are built up from a number of identical simpler molecules, a polymer (Greek polloi, many), each of the component parts of which is a monomer (Greek monos, alone). The number of units can be given by a prefix: dimer, a molecule formed from two identical smaller molecules; trimer, three; and so on. An oligomer (Greek oligoi, few) has relatively few such units. Some refer to molecules that are closely related: isomers (Greek isos, equal) are compounds with the same formula but different arrangements of atoms and different properties; enantiomers (Greek enantios, opposite), are pairs of molecules that are mirror images of each other.

Related adjectives are formed in ‑meric: dimeric, isomeric, polymeric. Adjectives formed in ‑merous refer to an organism made up of a given number of parts: heptamerous (Greek hepta, seven), having parts arranged in groups of seven; polymerous, having or consisting of many parts; isomerous, having or composed of parts that are similar in number or position.

Terms in ‑mere refer to elements of biological structures, as in telomere (Greek telos, end), a compound structure at the end of a chromosome; and blastomere (Greek blastos, germ, sprout), a cell formed by cleavage of a fertilized ovum. Related adjectives here are formed in ‑meric: centromeric, telomeric.