1. a combining form meaning straight, correct, or right; used in chemistry to denote a benzene ring with substituents in adjacent positions
Usage: productive prefix in scientific and technical terminology

1. short for orthodontics or an orthodontist
Usage: informal; common in dental contexts

1. relating to or denoting orthodontics or orthodontic treatment
Usage: informal; used attributively

Examples

• The prefix ortho- appears in words like orthopedic and orthography.
• She went to ortho to get her braces adjusted.
• My ortho appointment is scheduled for next Tuesday.
• The ortho treatment took about two years to complete.
• Ortho-substituted benzene rings have different chemical properties than para-substituted ones.