Try Our Apps
35 Words that Change History
an alteration in the colour of certain substances as a result of being exposed to light of different wavelengths
the reversible loss of colour of certain dyestuffs when illuminated at a particular wavelength
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
Cite This Source
Discover our greatest slideshows
8 Wintry Words
8 Words for Celebration
8 Offbeat Literary Genres to Get...
Decode the pieces of our favorite...
Browse more topics on our blog
What Is the Difference Between Discreet and Discrete?
Learn the correct uses of these two commonly confused homophones.
What Character Was Removed from the Alphabet?
What mistaken pronunciation gave this character its name?
This small mark has two primary uses: to signify possession or omitted letters.
How Do I Get a Word into the Dictionary?
People invent new words all the time, but which ones actually make it?
Word of the Day
Word Value for
Words With Friends
Nearby words for phototropy