Ortho (from the Greek word ????? 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, is a waveguide component
• An Orthochromatic spectrum is any spectrum of light devoid of red.

In cartography

• Orthophotography, aerial photography

In math

• Orthogonality
• Orthonormality

In computer science

• Orthographic projection, a means of representing a three-dimensional (3D) object in two dimensions (2D).

In medicine

• Orthodontics, a specialty of dentistry concerned with the study and treatment of malocclusions
• Orthopedic, the study of the musculoskeletal system.
• Ortho-DOT, a psychedelic drug
• Ortho-cept and Ortho Tri-cyclen, kinds of oral contraceptive drug

Corporations

• Ortho Pharmaceutical, which merged into Ortho-McNeil Pharmaceutical before being bought by Johnson & Johnson
• Ortho-Clinical Diagnostics, another subsidiary of Johnson & Johnson

See also

• Orthos