A chief mate (C/M) or chief officer, usually also synonymous with the first mate or first officer, is a licensed mariner and head of the deck department of a merchant ship. The chief mate is customarily a watchstander and is in charge of the ship's cargo and deck crew. The actual title used will vary by ship's employment, by type of ship, by nationality, and by trade: for instance, "chief mate" is not usually used in the Commonwealth, although "chief officer" and "first mate" are; on passenger ships, the first officer may be a separate position from that of the chief officer that is junior to the latter.