Ortho (from the Greek word ὀρθός meaning "straight" or "correct") may refer to: In science An arene substitution pattern in which two substituents occupy adjacent positions on an aromatic ring A prefix formally used to indicate the most hydrated form of an acid Ortho Mode Transducer,'s a waveguide component An Orthochromatic spectrum's any spectrum of light devoid of red. In cartography Orthophotography, aerial photography In math Orthogonality Orthonormality… (More on Ortho)