- A brownish monkey(Macaca mulatta) of India, used extensively in biological and medical research. 恒河猴，猕猴：印度的一种浅棕色猴（猕猴） ，广泛用于生物和医学研究
- orthogenesis
- orthogonal
- orthogonal projection
- orthogonals
- orthographic
- orthographical
- orthographic projection
- orthographies
- orthography
- orthomolecular
- orthopaedics
- orthopedics
- orthopsychiatry
- orthopteran
- orthopterans
- orthoptics
- orthorhombic
- orthoscopic
- orthostatic
- orthotics
- orthotropic
- orthotropous
- orting
- Ortles
- ortolan