[くろうと, kurouto](n, adj-no) (1) expert (professional) in a given trade or profession; (2) woman in the nightlife business; demimondaine; (P)[Add to Longdo]
[じかやくろう, jikayakurou](n) (something that is) available for use at any time; (someone who is) at one's beck and call; (something over which) one has complete mastery[Add to Longdo]
[わかいときのくろうはこうてもせよ, wakaitokinokurouhakoutemoseyo](exp) spare no effort while you are young; heavy work in youth is quiet rest in old age[Add to Longdo]