and 
if their ratio 
remains constant as and 
are varied. [M1.1]
describes: two variables and if their ratio remains constant as and are varied. [M1.1]
is symbolized: by 
[M1.1]
generally is abbreviated: to 'proportional'. [M1.1]
See constant of proportionality.
Contrast with inversely proportional.
Copyright 1997, The Open University