/ ˈmɑːstəri; NAmE ˈmæst-/ noun
1.
[ U , sing. ] mastery (of sth) great knowledge about or understanding of a particular thing
SYN command :
She has mastery of several languages.
2.
[ U ] mastery (of / over sb/sth) control or power :
human mastery of the natural world
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WORD ORIGIN
Middle English : from Old French maistrie , from maistre master.