First person singular, aorist indicative active, of Attic ξυνίημι = συνίημι (cf. xi 142, and for the gloss sigma 1553). Evidently quoted from somewhere, perhaps Attic tragedy; Aeschylus has several instances, but NB also συνῆκα in Euripides, Andromache 919, glossed in Hesychius with ἔγνων .