Orthogonality comes from the Greek orthos, meaning "straight", and gonia, meaning "angle". It has somewhat different meanings depending on the context, but most involve the idea of perpendicular, non-overlapping, or uncorrelated.
In mathematics, two lines or curves are orthogonal if they are perpendicular at their point of intersection. Two vectors are orthogonal if and only if their dot product is zero. In computer science, orthogonality has to do with the ability of a language, method, or object to vary without side effects.
Orthogonality is a concept that has undergone a huge amount of generalization in mathematics, science, and engineering over the many centuries of time since the Ancient Babylonians, Ancient Egyptians, and Ancient Greeks. Much of this generalization has happened since the beginning of the 16th Century, and much of it has involved the concepts of mathematical functions and calculus.
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