Abaft means toward the stern of a vessel, always used relative to a specific reference point rather than as a standalone direction.
How It’s Actually Used
Abaft is almost always paired with a reference point: “abaft the beam” means behind the midpoint (beam) of the ship — commonly used to describe the bearing of another vessel or object, as in “a ship was sighted abaft the beam to starboard,” meaning behind the midpoint on the right side.
Abaft vs Aft
- Aft — a general direction, “toward the stern,” used without needing a specific reference point (“walk aft”)
- Abaft — specifically relative, “behind [some named point]” — you can’t just say “go abaft” the way you’d say “go aft”
Common Use in COLREGs
“Abaft the beam” appears specifically in COLREGs when defining the sectors for navigation lights — a vessel’s sternlight, for instance, is visible over an arc that includes the area abaft the beam, making this precise terminology genuinely load-bearing for correctly interpreting light and sound signal rules, not just descriptive color.
Exam Relevance
Correct use of “abaft” — particularly “abaft the beam” in the context of navigation light arcs and bearing descriptions — is tested in Navigation and COLREGs sections of deck officer competency exams.