Ἰσθμ-ιάς · Isthm-ias — LSJ
pecul. fem. of foreg., νίκα Pi. I. 8(7).3; αἱ Ἰ. σπονδαί Th. 8.9.
ἡ Ἰ. (sc. ἑορτή) the Isthmian festival, Pl.Com. 46.10: pl., αἱ Ἰσθμιάδες,= τὰ Ἴσθμια, Pi. O. 13.33; a period of two years, between each celebration of the games, Apollod. 2.7.2.