epistrophe n.

before vowels reduced to ep-, before aspirated vowels eph-, word-forming element meaning "on, upon, above," also "in addition to; toward, among," from Greek epi "upon, at, close upon (in space or time), on the occasion of, in addition," also "after," from PIE *epi, *opi "near, at, against" (source also of Sanskrit api "also, besides;" Avestan aipi "also, to, toward;" Armenian ev "also, and;" Latin ob "toward, against, in the way of;" Oscan op, Greek opi- "behind;" Hittite appizzis "younger;" Lithuanian ap- "about, near;" Old Church Slavonic ob "on"). A productive prefix in Greek; also used in modern scientific compounds (such as epicenter).

Proto-Indo-European root meaning "to wind, turn."

It forms all or part of: anastrophe; antistrophe; apostrophe (n.1); apostrophe (n.2); boustrophedon; catastrophe; epistrophe; strabismus; strap; strep; strepto-; streptococcus; streptomycin; strobe; strobic; stroboscope; strop; strophe; strophic.

It is the hypothetical source of/evidence for its existence is provided by: Greek strophe "stanza," originally "a turning," strephein "to turn," strophaligs "whirl, whirlwind," streblos "twisted," stremma "that which is twisted."