# Disjunction

In Logic the term ‘disjunction’ is used to designate one of five functions
in Propositional Logic where *at least one* atomic
propositions that compose a compound proposition is
true.
For example, take the following two simple propositions:

- Kato is a dog.
- Kato is a mammal.

These two simple (or *atomic*)
propositions can be *disjoined* to form the **compound proposition**, Kato is a dog *or* Kato is a mammal.
By disjoining the simple propositions into a single compound proposition we are claiming that one of the elements is true (and it
does not matter which).
Every proposition, whether simple or compound, has a truth value, the
disjunction of two propositions will be true
in all cases but one: when *neither component is true*.

In ordinary language there are different words that serve the logical function of disjunction: ‘or’ and ‘unless’, etc.