掌握 (zhǎng wò) means “to grasp (often fig.); to control; to seize (initiative, opportunity, destiny); to master; to know well; to understand sth well and know how to use it; fluency”. It is an HSK 5 Chinese word in the HSK 3.0 vocabulary.
他已经掌握了三门外语。
Tā yǐjīng zhǎngwò le sān mén wàiyǔ.
He has already mastered three foreign languages.
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