Source : Webster's Revised Unabridged Dictionary (1913)

Spectrophotometry \Spec`tro*pho*tom"e*try\, n.
   The art of comparing, photometrically, the brightness of two
   spectra, wave length by wave length; the use of the
   spectrophotometer. -- {Spec`tro*pho`to*met"ric}, a.