/mas"teuh ree, mah"steuh-/ , n. , pl. masteries for 1-4.
1. command or grasp, as of a subject: a mastery of Italian.
2. superiority or victory: mastery over one's enemies.
3. the act of mastering.
4. expert skill or knowledge.
5. the state of being master; power of command or control.
[ 1175-1225; MASTER + -Y 3 ; r. ME maistrie ]