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degree-day

or de·gree day

[dih-gree-dey]
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noun Engineering.
  1. one degree of departure, on a single day, of the daily mean temperature from a given standard temperature. Abbreviation: dd

Origin of degree-day

First recorded in 1925–1930
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for degree-day

degree-day

noun
  1. a unit used in estimating fuel requirements in heating buildings. It is equal to a fall of temperature of 1 degree below the mean outside temperature (usually taken as 18°C) for one day
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

degree-day in Science

degree-day

  1. A unit of measurement equal to a difference of one degree between the mean outdoor temperature on a certain day and a reference temperature. The unit is most often used in estimating the energy needs for heating or cooling a building (for example, heating degree-days and cooling degree-days). Originally, degree-days were used to determine the relationship between temperature and plant growth. The term continues to be used in life sciences as a measure of upper- and lower-temperature limits for organisms.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.