sumuuntuu

Sumuuntuu is a Finnish verb meaning “to fog up” or “to become cloudy or hazy.” It is used to describe surfaces such as windows or lenses that accumulate moisture and grow less clear, as well as air or visibility that becomes hazier, and it can also be used figuratively to describe a moment when thoughts or perception lose clarity.

The verb is intransitive and forms from the noun sumu meaning fog with the verb-forming suffix -untua. In standard Finnish, the present tense is sumuuntuu, the past tense sumuuntui, and the past participle sumuuntunut. The noun form for the process is sumuuntuminen.

Usage examples: Ikkuna sumuuntuu, kun huone on lämmin ja kostea. Linssit sumuuntuvat kylmässä kelissä. Pitkän päivän jälkeen mieli sumuuntuu, ja ajatukset ovat epäselviä. (The window fogs up when the room is warm and humid; lenses fog up in cold weather; after a long day the mind clouds over and thoughts are unclear.)

Etymology and related terms: The term is derived from sumu (fog) with the -untua suffix. Related terms include sumu (fog) and tiivistyä (to condense). In meteorology and everyday language, sumuuntuminen refers to the process of fogging or hazing, and the concept is closely linked to condensation and reduced visibility.