In biology a tagma (Greek: τάγμα, plural tagmata - τάγματα) is a specialized grouping of multiple segments or metameres into a coherently functional morphological unit. Familiar examples are the head, the thorax, and the abdomen of insects. The metameres within a tagma may be either fused (such as in the head of an insect or a mammal) or so jointed as to be independently moveable (such as in the abdomen of most insects). Usually the term is taken to refer to tagmata in the morphology of members of the phylum Arthropoda, but it applies equally validly in other phyla, such as the Chordata.