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

• demand note
• demand-pull inflation
• quadrat
• quadrate
• quadratic
• quadratic equation
• quadratic polynomial
• quadratics
• quadrature
• quadrennial
• quadrennium
• quadri-
• quadric
• quadric surface
• quadriceps
• quadriceps femoris
• quadriga
• Quadrigesima Sunday
• quadrilateral
• quadrille
• quadrillion
• quadrillionth
• quadripara
• quadripartite
• quadriphonic