Learn Croatian: Ova pisma su nova. - These letters are new.

They look like feminine singular words, but they are actually neuter plural! The singular word for letter is pismo, which is neuter because it ends in '-o'. In Croatian, neuter nouns change their '-o' or '-e' ending to '-a' when there is more than one.

So do adjectives and pronouns always match that neuter plural '-a' ending?

Exactly! Any word describing a neuter plural noun must also take the neuter plural ending, which is '-a'. That is why we use ova (these) instead of ovo (this), and nova (new) instead of novo.

How would I say 'This letter is new' in the singular?

You would say Ovo pismo je novo. Notice how the neuter singular words end in '-o' instead of '-a', and the verb changes from the plural su (are) to the singular je (is).

Why is the verb su the third word? I thought short verbs had to be exactly in the second spot.

The word su is a clitic, which usually takes the second position in a sentence. However, it counts logical grammatical units rather than single words. Ova pisma (these letters) forms a single, unbreakable unit (the subject), so su naturally goes right after it.