Learn Finnish: Uusi kampaus pehmentää kasvojasi. - The new hairstyle softens your face.

It comes from the adjective pehmeä (soft). By dropping the final vowel -ä and adding the transitive suffix -ntää, we get pehmentää, which means "to make (something) soft" or "to soften." This directly applies the pattern of turning an adjective into an active, state-changing verb.

Why is the object kasvojasi in the partitive case here instead of the accusative?

Verbs that describe a visual effect, an ongoing process, or an abstract influence usually take a partitive object. Because the hairstyle is continuously softening the face's appearance, rather than completing a literal physical transformation, kasvojasi must be in the partitive.

The English translation says "face" (singular), but kasvojasi is grammatically plural. Why?

The Finnish base word for face, kasvot, is a plural-only word (just like "scissors" or "glasses" in English). Because of this, its partitive form kasvoja is built in the plural. The -si at the end is simply the possessive suffix meaning "your".

Is the noun kampaus (hairstyle) derived from another word?