Definition
A number less than zero, written with a minus sign in front of it (for example, -5 or -12.4). Negative numbers represent quantities below a chosen reference point, such as temperatures below zero, voltages opposite to a reference polarity, or values that fall below a baseline.
Plain English
Any number smaller than zero. It is written with a minus sign, like -3 or -20, and stands for something that is below the starting point you are measuring from.
Context Anchor
Seen in aviation maintenance math, temperature readings, electrical measurements, and corrections where values may be above or below zero.
Derivation
From the Latin negare, meaning 'to deny' or 'to say no.' A negative number 'denies' or reverses a positive value — it points the opposite way on the number line.
Why Pilots Care
Sign errors in maintenance calculations (weight and balance, electrical readings, temperature corrections) can flip a result entirely. Knowing whether a number is positive or negative determines whether you add or subtract, climb or descend, charge or discharge.
Analogy
Think of zero as ground level on a number line. Positive numbers are above it, and negative numbers are below it.
Intuition Check
Negative does not mean “bad” here. It means the number is less than zero, or opposite to the direction being treated as positive.
Example Sentence 1
The outside air temperature at cruise altitude was a negative number, around -40 degrees, so the technician checked the anti-icing system before dispatch.
Example Sentence 2
A negative number appeared in the moment column during the weight-and-balance check.