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

• Ageratum houstonianum
• Aggeus
• aggie
• agglomerate
• agglomerated
• agglomeration
• agglomerative
• agglomerator
• agglutinate
• agglutinating activity
• agglutination
• agglutination test
• agglutinative
• agglutinin
• agglutinogen
• aggrade
• aggrandise
• aggrandisement
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• aggravate
• aggravated
• aggravated assault
• aggravating
• aggravatingly