patina
Merriam-Webster's Word of the Day for September 11, 2026 is: patina • \puh-TEE-nuh\ • noun A patina is a usually green film that forms on copper and bronze that is exposed to moist air for an extended time. The word patina can also refer to a shiny or dark surface that over time forms naturally on something (such as wood or leather), or to a literal or figurative thin layer.