ketch vs. sloop

a sailing vessel rigged fore and aft on two masts, the larger, forward one being the mainmast and the after one, stepped forward of the rudderpost, being the mizzen or jigger.

a single-masted, fore-and-aft-rigged sailing vessel, with or without a bowsprit, having a jib-headed or gaff mainsail, the latter sometimes with a gaff topsail, and one or more headsails. Compare cutter ( def 3 ), knockabout ( def 1 ).