met(a)- Also m-.
Change of position or condition; behind, after, or beyond; of a higher or second-order kind; chemical substitution.
[Greek meta, with, across, or after.]
The principal sense in classical Greek was change or transformation; this occurs in a variety of English words, such as metamorphosis (Greek morphē, form), a change of the form or nature of a thing or person into a completely different one; metabolism (Greek metabolē, change), the chemical processes that occur within a living organism in order to maintain life; and metathesis (Greek, from metatithenai, transpose, change the position of), the transposition of sounds or letters in a word.
Other senses have developed in English. One is that of position behind, after, or beyond another, as in metacarpus, the group of five bones of the hand between the wrist (carpus) and the fingers, or metatarsus (Greek tarsos, flat of the foot), the group of bones between the ankle and the toes.
The term metaphysics, the branch of philosophy that deals with the first principles of things, was interpreted to mean a subject that is beyond or transcends physics. Other terms have since been formed with this sense of a a higher level or something once removed: metalanguage, a form of language used to describe or analyze another language; metapsychology, speculation concerning mental processes and the mind-body relationship, beyond what can be studied experimentally.
In chemistry, meta-, usually abbreviated to m-, refers to substitution at two carbon atoms in a benzene ring that that have one other carbon atom between them: meta-xylene; metadichlorobenzene; metanilic acid, a dyestuff intermediate. See also ortho- and para-1. A few names refer to polymers: metaldehyde, a solid made by polymerizing acetaldehyde, used in slug pellets and as a fuel for portable stoves; metaphosphoric acid, a glassy deliquescent polymeric solid obtained by heating orthophosphoric acid.