Informal Definition
Modern texts on logic typically take as primitive some subset of the connectives: conjunction, or Kpq; disjunction, or Apq; negation, Np, or Fpq; or material conditional, or Cpq; and possibly the biconditional, or Epq. These connectives are functionally complete. However, they do not form a minimal functionally complete set, as the conditional and biconditional may be defined as:
So is also functionally complete. But then, can be defined as
can also be defined in terms of in a similar manner.
It is also the case that can be defined in terms of as follows:
No further simplifications are possible. Hence and one of are each minimal functionally complete subsets of .
Read more about this topic: Functional Completeness
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