Definition
A dot written in a number to separate the whole-number part on its left from the fractional part on its right, where each place to the right represents tenths, hundredths, thousandths, and so on.
Plain English
The small dot in a number that shows where the whole number ends and the fraction begins. The digits after the dot stand for parts of one whole.
Context Anchor
Pilots see decimal points in radio frequencies, altimeter settings, distances, fuel amounts, weights, and performance charts.
Derivation
From the Latin 'decimus' meaning 'tenth.' A decimal point marks the boundary between whole units and tenths, so the name simply reflects what the dot does.
Why Pilots Care
Misreading or misplacing a decimal point can cause major errors -- a frequency tuned wrong, a weight calculated ten times too high, or a fuel figure off by a factor of ten. Aviation numbers are unforgiving of decimal mistakes.
Intuition Check
Do not treat the decimal point as ordinary punctuation. It is part of the number, and moving it changes the number’s value.
Example Sentence 1
She tuned the tower frequency 118.3, careful to enter the digits on either side of the decimal point correctly.
Example Sentence 2
The manifold pressure gauge read twenty four point five inches.