The unofficial, yet commonly used, naval term ‘young gentleman’ referred to a commissioned officer-in-training. The appellation encompassed a variety of ratings including the entry-level positions of captain's servant (before 1794) and 1st-class volunteer (after 1794), as well as the ratings of midshipman and master's mate, which often, but not always, denoted more experienced trainees. It was also common for a young gentleman to appear on a ship's muster book in other ratings such as ‘able seaman’, ‘ordinary seaman’, or any petty officer designation. Under the mantle of officers-in-training, the system of rating was fluid and, to a large extent, meaningless. Most muster books showed frequent changes in a young gentleman's rating which could transition from midshipman, to master's mate, to able seaman, and back to midshipman, all within the space of a year. As long as a recruit could prove six years in the service, two of which had been spent in the rating of midshipman or master's mate, he would be eligible to sit the examination for lieutenant, which opened opportunities for advancement to commissioned rank.

For much of the eighteenth century the assignment of entry-level ratings was arbitrary and at the discretion of recruiting captains. A twelve-year-old Horatio Nelson entered the service as an able seaman, despite his lack of experience as a sailor and his ambitions for command. ‘Able’ was also the entry designation given to a fourteen-year-old John Jervis, who later became the Admiral Earl St Vincent.