ORMC - Pacinian corpuscle
- orthodigita
- orthodontia
- orthodontic appliance
- orthodontic attachment
- orthodontic band
- Orthodontic treatment (dental braces)
- orthodontic wire
- Orthodontics
- orthodontist
- orthodontology
- orthodox sleep
- orthodromic
- orthodromic atrioventricular reciprocating tachycardia
- orthogenesis
- orthogenic
- orthogenics
- orthoglycemic
- Orthognatha
- orthognathia
- orthognathic
- orthognathic surgery
- orthognathic, orthognathous
- orthognathism
- orthognathous
- orthogonal
- orthogonal lead system
- orthograde
- Orthohepadnavirus
- orthoiodohippurate
- orthokeratologist
- orthokeratology
- orthokeratosis
- orthokinetics
- ortholidine
- orthologous
- orthologous genes
- orthomechanical
- orthomechanotherapy
- orthomelic
- orthometer
