Definition
Any one of the ten symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9 used to represent numbers in the base-ten (decimal) numbering system.
Plain English
A single digit from 0 through 9. These are the ten basic number symbols used in everyday counting.
Context Anchor
Seen when reading or entering numbers in aviation, such as radio frequencies, transponder codes, altimeter settings, weights, and performance data.
Derivation
From the Latin decem, meaning ten, and digitus, meaning finger. People originally counted on their ten fingers, which is why the base-ten system uses ten distinct digits.
Why Pilots Care
Many cockpit entries are made one digit at a time. Reading or entering one decimal digit incorrectly can change a frequency, setting, or value.
Intuition Check
A decimal digit is not the decimal point. It is one number symbol, such as 7 in 118.7.
Example Sentence 1
A transponder code such as 1200 is made up of four decimal digits, each between 0 and 7.
Example Sentence 2
Altimeter settings always use decimal digits such as 3, 0, point, 0, 8.