Orthogonality is a term with various meanings depending on the context.

In mathematics, orthogonality is the generalization of the geometric notion of perpendicularity. Although many authors use the two terms perpendicular and orthogonal interchangeably, the term perpendicular is more specifically used for lines and planes that intersect to form a right angle, whereas orthogonal is used in generalizations, such as orthogonal vectors or orthogonal curves.

The term is also used in other fields like physics, art, computer science, statistics, and economics.