Merriam-Webster Collegiate Dictionary - orthogonal

 adjective  Etymology: Middle French, from Latin orthogonius, from Greek orthogonios, from orth- + gonia angle — more at -gon  Date: 1612  1.  a. intersecting or lying at right angles  b. having perpendicular slopes or tangents at the point of intersection ~ curves  2. having a sum of products or an integral that is zero or sometimes one under specified conditions: as  a. of real-valued functions having the integral of the product of each pair of functions over a specific interval equal to zero  b. of vectors having the scalar product equal to zero  c. of a square matrix having the sum of products of corresponding elements in any two rows or any two columns equal to one if the rows or columns are the same and equal to zero otherwise ; having a transpose with which the product equals the identity matrix  3. of a linear transformation having a matrix that is ~ ; preserving length and distance  4. composed of mutually ~ elements an ~ basis of a vector space  5. statistically independent  • ~ity noun  • ~ly adverb