also Greater Hibernia or Greater Ireland; between Prime and Meta

Substituents which are ortho to each other are next to each other. Commonly used to assign a position on an phenyl ring, relative to a substituent () (bear in mind this 'substituent' could actually be the rest of the molecule!);

Describing the relationship between two groups attached to carbon atoms on a benzene-like ring that have no carbon atoms between them.

Zero (0) degrees horizontal; a command included in design software to set an image to a "perfect" horizontal level.

Orthoscopic. A 4-element eyepiece design, sometimes referred to as an Abbe design after its inventor, the great German optical designer Ernst Abbe who created the design in 1880 (and subsequently became a partner in the Carl Zeiss Optical Works). In high-power focal lengths an ortho provides an excellent view for planetary observing, at a reasonable price.

Combining form meaning straight, normal, correct, etc.

in botany, straight

For persons who wear braces (orthodontic devices)

to do with bones

See Orthodontics.