Etymology

First coined to serve as an antonym of entropy, substituting its en- element (representing the prepositional prefix ἐν ‎(en), en, “in” in its Ancient Greek etymon ἐντροπία ‎(entropía), entropia, “a turning towards”) with ex- (representing the Ancient Greek ἐξ ‎(ex), ex, “out of”, “from”); because ἐξ ‎(ex) takes the form ἐκ ‎(ek) when prefixed to an element beginning with τ ‎(t), the analogical spelling is ectropy (or, alternatively, ektropy), as if after the Ancient Greek *ἐκτροπία ‎(ektropía, “a turning out of”).