In the United States, it means the lowest three enlisted rates of the U.S. Navy, followed by the higher petty officer ranks. The equivalent of the seaman is the matelot in French-speaking countries, and Matrose in German-speaking countries.
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. This is untrue in the US Navy where a sailor might be a seaman but not all US Navy sailors are seamen as they might be an Airman or Fireman. 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, 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.
Ordinary seaman or matelot de troisième classe in French
Able seaman or matelot de deuxième classe in French
Leading seaman or matelot de première classe in French
Master seaman or matelot-chef in French
The rank of master seaman is unique because it was created only for the Canadian Navy. It does not follow the British tradition of other Canadian ranks. It corresponds to the rank of master corporal/caporal-chef.
Matelot 2e classe (seaman 2nd class), or apprentice seaman, and matelot breveté (able seaman) are designations of the French Navy. Matelots are colloquially known as "mousses".
Matelot breveté (able seaman)
In the Royal Navy the rate is split into two divisions: AB1 and AB2. The AB2 rating is used for those who have not yet completed their professional taskbooks. The rate of ordinary seaman has been discontinued.
The actual title for an E-3 in the U.S. Navy varies based on the subset of the Navy or Coast Guard, also known as a group rate, to which the member will ultimately be assigned. Likewise, the color of his/her group rate mark also depends on that subset of the Navy or Coast Guard in which they're serving and which technical rating they will eventually pursue.
Those in the General Deck, Technical, Weapons and Administrative Group (with the exception of the Aviation Administrationmen) are called "seamen" and they represent the largest group of Navy and Coast Guard personnel in pay grades E-3 and below. They wear white stripes on their blue uniforms (USN + USCG), and navy blue (black) stripes on their white uniforms (USN only).
Those in the Medical Group are now called "hospitalmen." In October 2005, the USN Dental Technician (DT) rating was merged into the Hospital Corpsman (HM) rating, eliminating the "dentalman" title for E-3 and below. Those who once held the rank of "dentalman" have instead become "hospitalmen". With this merger, these personnel possess the only rating in this area of duty. They wear white stripes on their blue uniforms, and navy blue stripes on their white uniforms. This rating was previously called Pharmacist's Mate (PHM) and HMs are still colloquially referred to as "corpsman" in the naval service. Hospitalmen exist only in the U.S. Navy; their equivalent in the U.S. Coast Guard is the Health Services Technician (HS), which is sourced from seamen in that service's Administrative and Scientific Group.
Those in the shipboard Engineering and Hull Group, comprising conventional (USN + USCG) and nuclear (USN only) powerplants and propulsion, as well as the hull maintenance area, are called "firemen." They wear red stripes on both their USN and USCG blue uniforms and, in the case of the Navy, white uniforms.
Those in the Aviation Group of the Navy and Coast Guard are called "airmen", and they wear green stripes on blue uniforms (USN + USCG) and white uniforms (USN only).
Enlisted personnel in the Construction Group, which primarily populates the U.S. Navy's civil engineering construction battalions (i.e., Seabees), are called "constructionmen" and they wear light blue stripes on both their blue and white uniforms. Constructionmen are unique to the U.S. Navy; there is no U.S. Coast Guard equivalent.
No such stripes for E-1, E-2 or E-3 are authorized to be worn on working uniforms, e.g., NWUs (Navy Work Uniform), ODUs (USCG Operational Duty Uniform), coveralls, utility wear, flight suits, hospital and clinic garb, diving suits, etc. However, sailors with the rank of E-2 or E-3 are permitted to wear silver-anodized collar devices on their service uniforms.
Some sailors and coast guardmen receive a rating following completion of a military technical training course for that particular rating known as an "A" school. Other sailors and coast guardsmen who have completed the requirements to be assigned a rating and have been accepted by the Navy Personnel Command/Bureau of Naval Personnel (USN) or the Coast Guard Personnel Service Center Command (USCG) as holding that rating (a process called "striking") are called "designated strikers", and are called by their full rate and rating in formal communications (i.e., machinist's mate fireman (MMFN), as opposed to simply fireman (FN)), though the rating is often left off in informal communications. Those who have not officially been assigned to a rating are officially referred to as "undesignated" or "non-rates." In order to advance to the rate of petty officer third class, a seaman would have to submit a request every 6 months. However, advancement is not guaranteed because of the large numbers of seamen competing for a promotion.