In mathematics, two vectors are orthogonal if they're perpendicular, for example, they form a right angle. The word comes from the Greek ὀρθός (orthos), meaning "straight", and γωνία (gonia), meaning "angle". For example, a subway and the street above, although they don't physically intersect, are orthogonal if they cross at a right angle. Definitions Definition. Two vectors x and y in an inner product space V are orthogonal if their inner pro… (More on Orthogonal)