reduce (something) by (something)(redirected from reduce something by)
reduce (something) by (something)
To make something smaller, weaker, narrower, etc., by some amount, degree, or margin. The government has reduced our budget by nearly 25%. Even reducing the temperature on the thermostat by a few degrees could save you hundreds on your energy bill each month.
reduce something by something
to diminish something by a certain amount. I have to reduce your allowance by two dollars per week until you pay me back for the broken window. I will reduce the bill by a few dollars.