1. The ratio of the focal length to the diameter of a (camera) lens system
   - focal ratio, f number, speed

Derived forms: stop numbers

Type of: ratio

• antisubmarine
• antisyphilitic
• antitank
• antitauon
• antithesis
• antithetic
• antithetical
• antithetically
• antithyroid
• antitoxic
• antitoxin
• antitrade
• antitrade wind
• antitrades
• antitrust
• antitrust case
• antitrust law
• antitrust legislation
• antitumor
• antitumour
• antitussive
• antitype
• antitypic
• antitypical
• antivenene