In Logic the term ‘conjunction’ is used to designate one of five functions in Propositional Logic where any two atomic propositions that compose a compound proposition are simultaneously true.

For example, take the following two simple propositions:

  1. Kato is a dog.
  2. Kato is a mammal.
These two simple (or atomic) propositions can be conjoined to form the compound proposition, Kato is a dog and Kato is a mammal. By conjoining the simple propositions into a single compound proposition we are claiming that both elements are true.

But, since every proposition, whether simple or compound, has a truth value, the conjunction of two propositions will be true in only one case: when both component are true.

In ordinary language there are many different words that serve the logical function of conjunction: ‘and’, ‘but’, ‘yet’, ‘also’, ‘still’, ‘both’, ‘however’, ‘moreover’, ‘nevertheless’, ‘additionally’, etc. While these words have distinct meanings in ordinary language, in Propositional Logic they all perform the same logical function: connecting two simple propositions into a compound proposition.