Enemy (noun)

1. A person who one is hostile toward and seeks to harm.
2. A person or organization with conflicting interests or goals.
3. An opponent in a conflict, battle, or competition.
4. A force or power that opposes one's interests or goals.
5. A nation or group considered hostile or dangerous.

Origin:

Middle english enemi, from old french enemi, from latin inimicus, from in- + amicus friend.

Examples:

1. The two countries were enemies during the war.
2. He considers the thief to be his enemy.
3. The two teams were enemies on the playing field.
4. The enemy army was closing in.
5. The enemy was at the gate.