ally

1. To unite or form a connection between (people or things), as between families by marriage, or between states by confederacy, league, or treaty.
2. Chiefly followed by to or with: to connect or form a relation to (someone or something) by similarity in features or nature.
3. To join or unite (oneself or itself) against, with, etc., someone or something else.
4. Chiefly followed by with: to enter into an alliance or unite for a common aim.