πείρας

From LSJ

ἐν δὲ τοῖς φυσικοῖς ἀεὶ οὕτως, ἂν μή τι ἐμποδίσῃ → in natural products the sequence is invariable, if there is no impediment | now with that which is natural it is always thus if there is no impediment

Source

French (Bailly abrégé)

1ασα, αν;
part. ao. de πείρω.
2gén. sg. ou acc. pl. de πεῖρα.

Russian (Dvoretsky)

πείρας: ασα, αν part. aor. к πείρω.

Dutch (Woordenboekgrieks.nl)

πείρας -ασα -αν ptc. aor. act. van πείρω.