Definition of prime
1 a
often capitalized
:the second of the canonical hours
b
:the first hour of the day usually considered either as 6 a.m. or the hour of sunrise
3
:the most active, thriving, or satisfying stage or period
- in the prime of his life
4
:the chief or best individual or part :pick
- prime of the flock, and choicest of the stall
- —Alexander Pope
5
:prime number
6 a
:the first note or tone of a musical scale :tonic
b
:the interval between two notes on the same staff degree
7
:the symbol ′ used to distinguish arbitrary characters (such as a and a′), to indicate a specific unit (such as feet or minutes of time or angular measure), or to indicate the derivative of a function (such as p′ or f′(x)) — compare double prime
8
:prime rate
