What's the "een" in Halloween?
1560s, "relation of parts, proportion," from Latin symmetria, from Greek symmetria "agreement in dimensions, due proportion, arrangement," from symmetros "having a common measure, even, proportionate," from syn- "together" (see syn-) + metron "meter" (see meter (n.2)). Meaning "harmonic arrangement of parts" first recorded 1590s. Symmetrophobia is from 1809, supposed to be evident in Egyptian temples and Japanese art.
symmetry sym·me·try (sĭm'ĭ-trē)
Exact correspondence of form and constituent configuration on opposite sides of a dividing line or plane or about a center or an axis.
in biology, the repetition of the parts in an animal or plant in an orderly fashion. Specifically, symmetry refers to a correspondence of body parts, in size, shape, and relative position, on opposite sides of a dividing line or distributed around a central point or axis. With the exception of radial symmetry (see below), external form has little relation to internal anatomy, since animals of very different anatomical construction may have the same type of symmetry