Mastery (noun)

1. The state of being a master of something.
2. Great skill or knowledge in a particular subject or activity.
3. Control or dominance over something.

Origin:

Middle english: from old french maistrie, from maistre (see master).

Examples:

1. He has achieved mastery of his craft.
2. She demonstrated mastery of the language.
3. He has gained mastery over his emotions.
4. The mastery of the technique requires years of practice.
5. The mastery of the game is evident in his play.