26-letter words containing f, e, a, s, t
- won't/wouldn't hear of sth — If you say that you won't hear of someone doing something, you mean that you refuse to let them do it.
- zermelo fränkel set theory — (mathematics) A set theory with the axioms of Zermelo set theory (Extensionality, Union, Pair-set, Foundation, Restriction, Infinity, Power-set) plus the Replacement axiom schema: If F(x,y) is a formula such that for any x, there is a unique y making F true, and X is a set, then {F x : x in X} is a set. In other words, if you do something to each element of a set, the result is a set. An important but controversial axiom which is NOT part of ZF theory is the Axiom of Choice.