Definition
The horizontal direction in which the longitudinal axis of an aircraft is pointed, expressed in degrees from north (000° to 360°), measured clockwise. Heading refers to where the nose is pointed, not necessarily the path the aircraft is travelling over the ground.
Plain English
The compass direction the nose of the aircraft is pointing, given as a number of degrees from north.
Context Anchor
You see heading during straight-and-level flight, on the compass or heading indicator, and whenever an instructor or controller tells you to fly or hold a certain direction.
Derivation
From the everyday sense of 'heading somewhere' — the direction you are facing or going. In aviation, it is tightened to a precise numerical direction the nose is pointed, measured in degrees from north.
Why Pilots Care
Precise heading control keeps the aircraft on the intended path; failure to maintain it produces drift and navigation errors.
Intuition Check
Do not assume heading means the whole route or the place you are trying to go. In flying, heading means the direction the airplane is pointed right now.
Example Sentence 1
ATC instructed the pilot to turn right and fly a heading of 090.
Example Sentence 2
In straight-and-level flight the student practiced changing heading smoothly without altitude or airspeed change.