Two quantities 
and 
are said to be directly proportional, proportional, or "in direct proportion"
if 
for a nonzero constant of variation 
. This relationship is commonly written
.
Directly Proportional
See also
Constant of Variation, Direct Variation, Inversely Proportional, ProportionalExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Directly Proportional." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/DirectlyProportional.html