Able seaman is a military rank used in naval forces.
In 1653 the Royal Navy introduced a new pay scale as part of reforms following defeat in the Battle of Dungeness the previous year. Included in these reforms were, for the first time, separate pay scales for more experienced seamen. It distinguished between an ordinary seaman and an able seaman. The higher ranked able seaman was required to be competent in steering, use the lead and working aloft, and received about 25% higher pay than an ordinary seaman.
In the middle of the 18th century, the term "able seaman" (abbreviated AB) referred to a seaman with more than two years' experience at sea and considered "well acquainted with his duty". Seamen with less experience are referred to as landmen (for the first year at sea) or ordinary seamen (for the second).
In time of war (such as the Seven Years' War or the Napoleonic Wars), with many more warships in service, the navy, merchant marine, and privateers competed ferociously for the limited pool of able seamen, leading to the unpopular use of impressment by the Royal Navy to keep its ships manned. In peacetime, with fewer active warships, there was usually a surplus of unemployed able seamen willing to work in the navy. As late as the Napoleonic Wars, the Royal Navy's practice of stopping American ships to press American sailors into involuntary service was one of the main factors leading to the War of 1812 with the United States.
In the Royal Canadian Navy, Sailor Second Class (previously Able Seaman until August 2020) is the second-lowest of the non-commissioned member ranks, ranking above Sailor Third Class and below Sailor First Class. Sailors Second Class wear a single gold chevron, point down, as an insignia of rank; it is worn on the upper part of both sleeves of the service dress tunic, and on slip-ons on both shoulders on other uniforms.
In all trades, the rank is awarded on completion of 30 months of service, by which time all initial training is completed. Consequently, it is sometimes said that promotion to the rank of Sailor Second Class means the recipient has lost their 'best excuse', on the theory that Sailors Third Class are generally assumed to know nothing.
Able seaman is the equivalent rank to Leading aircraftman, in the Royal Australian Air Force and Private Proficient in the Australian Army. It is not equivalent to Lance Corporal which is rated as E4, not E3 like the ranks of Able Seaman and Leading Aircraftsman.
Able Seamen with additional skills are denoted by modifications to the "AB" rank; for example photography skills which are acknowledged in the title Able Seaman Imagery Specialist, or ABIS.