The property of certain radiation, especially ultraviolet light, to cause chemical changes in materials.
From Greek 'aktis' (ray) + '-ism' (system or practice). The term was coined in the 1800s when scientists first observed that light rays could trigger chemical reactions.
Actinism is why old photographs fade, why sunscreen protects you, and why plants evolved pigments—ultraviolet rays aren't just light, they're actually little energy packets that can break chemical bonds and change matter itself.
Complete word intelligence in one call. Free tier — 50 lookups/day.