Liddell–Scott–Jones: ἰᾰχ-ή

ἰᾰχ-ή,ἡ,

A. cry, shout, both of victor and vanquished, Il. 15.396 , etc.;wail, shriek, Od. 11.43 ; also,a joyous sound, ἰαχὰ ὑμεναίων

Pi. P. 3.17

, cf. E. Tr. 337 (lyr., pl.); κροτάλων τυπάνων τε

h.Hom. 14.3

; αὐλῶν

Lyr.Adesp. 96

; συρίγγων

E. IA 1039

(lyr.): in pl., generally,shouts of joy, Thgn. 779 , E. Ba. 149 (lyr.); butπολύδακρυς ἰ. A. Pers. 940 , cf. E. El. 142 , Ph. 1302 (all lyr.). (ϝι-, cf. Il. 4.456 : a vowel is not elided before it in Ep. exc. in h.Hom. 14.3 , Hes. Th. 708 , Sc. 404 : Trag. only in lyr.; for the quantity cf. foreg.)