Definition
The angle which, when added to a given angle, produces a sum of 180 degrees. Two angles are supplementary when their measures total 180 degrees.
Plain English
The supplement of an angle is whatever angle you'd need to add to it to reach 180 degrees. So the supplement of 120 degrees is 60 degrees, because 120 + 60 = 180.
Context Anchor
Seen in basic navigation, flight computer work, and geometry used to describe directions or angles.
Derivation
From the Latin supplementum, meaning 'something added to fill up.' The supplement is the angle added to fill the gap up to a straight line (180 degrees).
Why Pilots Care
Pilots may meet this term when working with angles in navigation problems or training material. Knowing it prevents a simple math word from slowing down the larger aviation concept.
Grounding Statement
Picture a straight line as 180 degrees; the supplement is whatever angle is still needed to complete that straight line.
Intuition Check
“Supplement” does not mean an extra booklet or added reading here. It means the angle needed to complete a total of 180 degrees.
Example Sentence 1
If one angle of a triangle measures 110 degrees, its supplement is 70 degrees.
Example Sentence 2
Knowing the supplement of the heading change allowed the pilot to visualize the remaining turn to a reciprocal course.