<synset id="n13821408" type="n">
<lex_filenum>24<lex_filenum/>
<word lex_id="0">focal ratio<word/>
<word lex_id="0">f number<word/>
<word lex_id="0">stop number<word/>
<word lex_id="0">speed<word/>
<pointer refs="n13819207">Hypernym<pointer/>
<def>the ratio of the focal length to the diameter of a (camera) lens system<def/>
<synset/>