isomeric adj.

before vowels often is-, word-forming element meaning "equal, similar, identical; isometric," from Greek isos "equal to, the same as; equally divided; fair, impartial (of persons); even, level (of ground)," as in isometor "like one's mother." In English used properly only with words of Greek origin; the Latin equivalent is equi- (see equi-).

Proto-Indo-European root meaning "to get a share of something." 

It forms all or part of: demerit; emeritus; isomer; isomeric; meretricious; merism; meristem; merit; meritorious; mero-; monomer; Moira; polymer; turmeric.

It is the hypothetical source of/evidence for its existence is provided by: Greek meros "part, lot," moira "share, fate," moros "fate, destiny, doom;" Hittite mark "to divide" a sacrifice; Latin merere, meriri "to earn, deserve, acquire, gain."

1852, in chemistry, back-formation from isomeric. A compound identical or nearly so in composition and molecular weight with another, but having different properties.