- Orthoclase Noun Adj
- Orthocomplement Noun
- Orthocomplementation Noun
- Orthocoupler Noun Adj
- Orthodentin Noun
- Orthodiagram Noun Adj
- Orthodiagraph Noun Adj
- Orthodiagraphy Noun
- Orthodontia Noun
- Orthodontics Noun
- Orthodontist Noun
- Orthodontology Noun
- Orthodoxy Noun Pnoun
- Orthodrome Noun Adj
- Orthoepist Noun
- Orthoepy Noun
- Orthoferrite Noun Adj
- Orthogenesis Noun
- Orthogeosyncline Noun
- Orthognathia Noun
- Orthognathism Noun
- Orthognathy Noun
- Orthogonal Adj Noun
- Orthogonality Noun
- Orthogonalization Noun
- Orthograde Adj Noun
- Orthographer Noun
- Orthography Noun
- Orthohydrogen Noun Adj
- Orthokeratinization Noun
- Orthokeratology Noun Adj
- Orthokeratosis Noun
- Ortholattice Noun Adj
- Orthology Noun Adj
- Orthometer Noun Adj
- Orthomyxovirus Noun Adj
- Orthonormality Noun Adj
- Orthonormalization Noun
- Orthopaedics Noun
- Orthopaedist Noun
- Orthopantomogram Noun Adj
- Orthopantomograph Noun Adj
- Orthopantomography Noun Adj
- Orthopedic Adj Noun
- Orthopedics Noun
- Orthopedist Noun
- Orthophony Noun
- Orthophoria Noun
- Orthophosphoric Adj Noun
- Orthophotograph Noun Adj Verb
- Orthophotomap Noun Adj
- Orthophyre Noun
- Orthopnea Noun
- Orthopnoea Noun
- Orthopolar Adj Noun
- Orthopole Noun Adj
- Orthopositronium Noun
- Orthopoxvirus Noun Adj
- Orthopraxia Noun
- Orthopraxy Noun