Ship of the line

A ship of the line was one powerful enough to take a place in the line of battle. (The term "battleship" has a similar etymology.) Generally, this meant a 3rd Rate or larger ship, with guns on two or more decks. Rated ships smaller than this were frigates, and carried all their guns on a single upper deck.

Rate	Guns	Men
1st Rate	100 or more	875 to 850
2nd Rate	90 to 98	700 to 750
3rd Rate	64 to 80	500 to 650
4th Rate	50 to 60	320 to 420
5th Rate	32 to 40	200 to 300
6th Rate	20 to 28	140 to 200
Sloops	16 to 18	90 to 125
Gun-Brigs & Cutters	6 to 14	5 to 25

The number of crew on a 1st Rate was increased by 25 when used as an Admiral's flagship, by 20 with a Vice Admiral and 15 with a Rear Admiral.

Originally from http://www.cronab.demon.co.uk/gen1.htm, with the author's permission.