Navy/ˈneɪvi/ Definition 1 of 4Pro Tip 1/3Naval Hierarchy The navy has ranks like admiral and captain, showing its structured leadership. His dream is to become a navy captain. Pro Tip 2/3Service Commitment Joining the navy often involves a long-term service commitment. After college, she'll commit to the navy for four years. Pro Tip 3/3Naval Operations The navy may undertake various operations like patrols, combat, and rescue missions. The navy's primary mission is to secure our territorial waters.