pho·​tol·​y·​sis fō-ˈtä-lə-səs How to pronounce photolysis (audio)
: chemical decomposition by the action of radiant energy (such as light)
photolytic adjective
photolytically adverb

Example Sentences

Recent Examples on the Web But sunlight in the upper atmosphere is continuously breaking down the gas by photolysis, so some process must be slowly replacing it. Davide Castelvecchi, Scientific American, 16 Dec. 2010

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'photolysis.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


New Latin

First Known Use

1903, in the meaning defined above

Time Traveler
The first known use of photolysis was in 1903

Dictionary Entries Near photolysis

Cite this Entry

“Photolysis.” Dictionary, Merriam-Webster, Accessed 28 Jan. 2023.

Medical Definition


pho·​tol·​y·​sis fō-ˈtäl-ə-səs How to pronounce photolysis (audio)
plural photolyses -ˌsēz How to pronounce photolysis (audio)
: chemical decomposition by the action of radiant energy compare radiolysis
photolytic adjective
photolytically adverb

More from Merriam-Webster on photolysis

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

The Great British Vocabulary Quiz

  • union jack speech bubble
  • Named after Sir Robert Peel, what are British police called?
Name That Thing

You know what it looks like… but what is it called?

Solve today's spelling word game by finding as many words as you can with using just 7 letters. Longer words score more points.

Can you make 12 words with 7 letters?