What does photochemically mean?
Photochemically is an adverb describing an action or process involving chemical change caused by light. It is commonly used in discussions of chemistry, biology, environmental pollution, photography, and materials that degrade under sunlight or ultraviolet radiation. For example, a substance may decay photochemically, meaning that exposure to light initiates chemical reactions that alter its composition or break it down. The term can also distinguish changes produced directly by light from ordinary thermal or chemical processes. Although “in light” may sometimes be sufficient in informal speech, “photochemically” makes the underlying mechanism explicit and is therefore especially common in scientific writing. It derives from the adjective photochemical, which combines the combining form “photo-” with “chemical,” and it should not be confused with merely photographic processes, which concern capturing images rather than causing chemical changes.
adverbIn a way that involves chemical changes brought about by light. The term is chiefly used in chemistry, biology, materials science, and environmental science.
- In a manner involving chemical reactions or changes caused by light.
"Some pollutants break down photochemically when exposed to sunlight."
"The coating is degraded photochemically by prolonged exposure to ultraviolet light."
"These microorganisms use the pigment to grow photochemically in the presence of sunlight."
Sunlight can be a chemical reagent: under the right conditions, it breaks molecules apart and drives reactions that would not otherwise occur.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does photochemically come from?
The word was formed in the early 20th century from photochemical, combining the combining form photo-, associated with light, with chemical. The underlying elements come from Greek phōs, meaning “light,” and the wider chemical vocabulary derived from Greek alchēmia, but the compound photochemical itself is an English formation. The adverb photochemically was created by adding the usual adverbial suffix -ly to that adjective.
Related word forms
How photochemically is actually used
This is a technical term used primarily in scientific and environmental contexts. It is more specific than saying that something happens “in the light,” because it explicitly identifies a light-induced chemical process.