Disjunction

Disjunction can refer to several things.

In logic, it can mean:
Inclusive disjunction (also known as logical or): at least one of the arguments is true
OR gate, the logic gate
Exclusive disjunction (also known as XOR): exactly one of the arguments is true

In biology, it can mean:
Meiosis, a type of cell division
Disjunct distribution, when populations of the same taxon are widely separated between two or more areas