Criteria for a Good Definition

  • Focus: a definition should exclude non-essentials. A separate discussion may be appropriate to describe implications, extensions, interpretations and other rationale, but the discussion must not alter the meaning of the definition itself. A good definition should be as concise as possible. 50 words is suggested as a target upper bound. (Excluding this final sentence, this paragraph contains 50.)
  • Common usage: if a term is already in common usage, the definition ought not conflict with common usage more than necessary. Some level of conflict may be unavoidable if common usage is ambiguous or unclear. This may be resolved by stating a preferred definition, while recognizing non-preferred variants, but the definition should not sanction incompatible interpretations.
  • Clarity and lack of ambiguity: given an arbitrary collection of entities, people from a wide range of perspectives, including both naïfs and experts, should largely agree on how the entities are grouped according to the definition.
  • The vish number of a good definition should be high, preferably infinite. [The vish number is a measure of the circumference of the vicious circle created when a definition ultimately refers to itself.]