Meaning of 使いこなす in Japanese

Definition of 使いこなす

つかいこなす(tsukaikonasu) 【使いこなす ·使い熟す】

(v5s, vt) to handle (men); to master (a tool); to manage; to acquire a command of (a language)
彼は英語をうまく使いこなす。
He has a good command of English.

妹いもうとは英仏えいふつ語ごを使いこなすつかいこなす。

My sister has a good command of both English and French.

彼かれは英語えいごをうまく使いこなすつかいこなす。

He has a good command of English.

He is second to none in his command of French.

彼のかれ英語えいごを使いこなすつかいこなす力ちからは私のわたしそれと等しいひとしい。

His command of English is on a par with mine.