Definition: 7.11: Prime Number
A prime number is one (which is) measured by a unit alone.
Modern Formulation
see prime numbers.
Notes
 Euclid defined the concept of a proper divisor (see part in Def 7.03), i.e. the divisors \(d\mid n\) with $d\neq n.$
 With this respect, his definition of prime numbers means literally: "A prime number is one which is measured by a unit as the only part."
Mentioned in:
Definitions: 1 2
Explanations: 3
Lemmas: 4
Proofs: 5 6 7 8 9 10 11 12
Propositions: 13 14 15 16 17 18
Solutions: 19 20
Theorems: 21
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References
Bibliography
 Scheid Harald: "Zahlentheorie", Spektrum Akademischer Verlag, 2003, 3rd Edition
Adapted from (subject to copyright, with kind permission)
 Fitzpatrick, Richard: Euclid's "Elements of Geometry"