ἅπαξ
ἅπαξ
a_copul and root παγ, πήγνυμι, cf. lat. simplex.
once, once only, once for all, like Lat. semel, Od., Hdt., Attic
c. gen., ἅπ. τοῦ ἐνιαυτοῦ once in the year, Hdt.
without any notion of number, after εἴπερ, ἤν, ἐπεί, ὡς, ὅταν, like Lat. ut semel, εἴπερ ἐσπείσω γʼ ἅπαξ if once you have made a treaty, Ar.; ὡς ἅπαξ ἤρξατο once he had begun, Xen.