ξένῳ δὲ σιγᾶν κρεῖττον ἢ κεκραγέναι → it's better for a stranger to keep silence than to shout (Menander)
Of persons: P. εὐμαθής.
Of things (capable of being imparted by teaching): P. and V. διδακτός, P. μαθητός, παιδευτός.