A definition assigns properties to some sort of mathematical object. For example, Euclid's Elements starts with a number of definitions, such as "a line is a breadthless length." After definitions, Euclid gives postulates or axioms. Based on these, he provides a number of proofs and constructions.
Definition
See also
Axiom, Postulate, ProofExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Definition." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Definition.html