- At a constant ratio (to). Two magnitudes (numbers) are said to be proportional if the second varies in a direct relation arithmetically to the first.
- The stopping distance is proportional to the square of the speed of the vehicle. — "How Far Will It Skid" at physicsclassroom.com.
- In proportion (to), proportionate. More common in US than UK.
- ...how much of the Bush administration's immediate post-9/11 emphasis on Iraq was appropriate and proportional to the overall picture of terrorism — Wikipedia:Foreign_policy_of_the_George_W._Bush_administration retrieved 24 Jan 2005.
at a constant ratio (to)