Meaning of dn/n among N molecules, how many are near probability that one molecule is near v proportional to avx fly dv dn(vr,vy,v =/()如yv,y,fvk Namong N molecules, how many are near v probability that one molecule is near v proportional to dvx ... ( ) x x f v dv Meaning of dn/N ( )d ( )d ( )d d ( , , ) x x y y z z x y z f v v f v v f v v N n v v v =  