Today's Word of the Day means...
radical (usually an alkyl or aryl group)
respiratory exchange ratio
or r roentgen
Abbreviation of radius
The symbol for resistance.
unit of X-radiation or gamma radiation, the amount that will produce, under normal conditions of pressure, temperature, and humidity, in 1 kg (2.2 lbs) of air, an amount of positive or negative ionization equal to 2.58104 coulomb. It is named for the German physicist Wilhelm Conrad Rontgen. See also rem.