Definition
In subtraction, the number that is taken away from another number. In the expression 10 − 3 = 7, the subtrahend is 3.
Plain English
The number you are subtracting. It's the amount being taken away from a larger number.
Context Anchor
Seen in aviation math, such as fuel, distance, weight, and performance calculations.
Derivation
From the Latin subtrahendus, meaning 'that which is to be taken away,' from sub- ('from under') and trahere ('to draw or pull'). It literally means the number to be drawn away from another.
Why Pilots Care
Using the wrong value as the subtrahend can reverse a calculation and give the wrong remaining fuel, distance, weight, or time.
Intuition Check
Do not confuse the subtrahend with the answer. In 10 - 3 = 7, 3 is the subtrahend, and 7 is the answer.
Example Sentence 1
When calculating remaining fuel, the fuel burned during the flight is the subtrahend taken from the starting fuel quantity.
Example Sentence 2
In the performance chart, subtract the temperature subtrahend from the standard value to obtain the corrected takeoff distance.