ἰδιοτροπία

A. peculiar quality, Cleom. 2.4, Ptol. Tetr. 1, Heph.Astr. 1.20, etc.
2. specific form or manner, Simp. in Ph. 1073.19; peculiarity, Dam. Pr. 90; idiosyncrasy, ib.388.
Liddell, Scott & Jones
A Greek-English Lexicon, 1940
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