ἑκούσιον
From LSJ
οὕτω τι βαθὺ καὶ μυστηριῶδες ἡ σιγὴ καὶ νηφάλιον, ἡ δὲ μέθη λάλον → silence is something profound and mysterious and sober, but drunkenness chatters
English (Strong)
neuter of a derivative from ἑκών; voluntariness: willingly.
Russian (Dvoretsky)
ἑκούσιον: τό свободная воля Plat., Arst.