what does the root ortho mean
home / medterms medical dictionary a-z list / ortho- (prefix) definition Medical Definition of Ortho- (prefix) Ortho- (prefix): Prefix meaning straight or erect. From the Greek orthos that means just that: straight or erect. Examples of terms involving ortho- include orthodontics (straightening the teeth), orthopaedics (straightening the child), orthopnea (breathing easily only in an upright position), orthostatic (an upright posture), etc.