Learn Finnish: Lapsuudessa kevät on aina kaunis. - In childhood, spring is always beautiful.

Words ending in -uus or -yys change their ending to -uude- or -yyde- before adding an ending like the "in" case (-ssa). So, the stem of lapsuus becomes lapsuude-, and then we add -ssa.

Why is Lapsuudessa at the beginning of the sentence?

Putting a time or place at the beginning of a sentence is very common in Finnish to set the scene. It translates naturally to "In childhood..." but you could also say Kevät on aina kaunis lapsuudessa (Spring is always beautiful in childhood).

There is no word for "the" or "a" before kevät. How do we translate it?

Finnish doesn't use articles like "a" or "the". The meaning is always figured out from context. Here, the sentence is making a general statement about the season, so simply using "spring" works best in English.

Why is kaunis in its basic dictionary form here?

Because the subject kevät (spring) is a regular, countable noun in its basic form, the describing word kaunis (beautiful) also stays in its basic dictionary form to match it.