partner

noun:a person who shares a legally recognized personal relationship, such as marriage, with another
- She celebrated her wedding anniversary with her partner, James.
noun:a person who collaborates with another in a business or professional venture
- The two engineers became partners in a start‑up that develops renewable energy technology.
noun:a teammate or companion in a game, sport, or other activity
- In doubles tennis, I always request a partner who has a strong serve.
noun:a member of a partnership firm who shares in the profits, losses, and management
- The accounting firm has three partners.
verb:to join with another person or organization in a partnership
- The university partnered with a tech company to develop an AI research lab.