Opponent

From the glossary of the Comprehensive Rules (November 20, 2020—Commander Legends)

Opponent

Someone a player is playing against. See rules 102.2 and 102.3.

From the Comprehensive Rules (November 20, 2020—Commander Legends)

• 102.2. In a two-player game, a player’s opponent is the other player.

From the Comprehensive Rules (November 20, 2020—Commander Legends)

• 102.3. In a multiplayer game between teams, a player’s teammates are the other players on their team, and the player’s opponents are all players not on their team.