extensionality

About 0.05 uses per million words.

Meaning

1. noun The principle that objects are equal if and only if their observed properties are the same, regardless of internal processes that lead to those properties.
2. noun The principle that functions are equal if and only if they operate on the same domain and for any given element of the domain the result of each of the functions is the same.
3. noun The principle, codified in the axiom of extensionality, that sets are equal if and only if they contain the same elements.

Similar words

indiscernibility of identicals law of identity univocity identity of indiscernibles universal equivalence principle identical identicalism analogism similarity

Often followed by

of and is for principle axiom in thesis condition