Seaman is one of the lowest ranks in a navy. In the Commonwealth it is the lowest rank in the navy, followed by able seaman and leading seaman, and followed by the petty officer ranks.

The term "seaman" is also a general-purpose for a man or a woman who works anywhere on board a modern ship, including in the engine spaces, which is the very opposite of sailing. Furthermore, "seaman" is a short form for the status of an "able-bodied seaman", either in the navies or in the merchant marines. An able-bodied seaman is one who is fully trained and qualified to work on the decks and superstructure of modern ships, even during foul weather,^[2] whereas less-qualified sailors are restricted to remaining within the ship during times of foul weather — lest they be swept overboard by the stormy seas or by the high winds.