Learn Croatian: Ako desni krvare, morate kupiti novu četkicu. - If the gums bleed, you must buy a new toothbrush.

You are probably used to desni as the masculine adjective for right (like in desni zavoj, right turn). However, it is also the noun for gums in the mouth. You have to rely on context—since directions don't bleed (krvare), it clearly means gums here!

Why does the verb krvare take the plural form?

Because desni (gums) is a feminine plural noun. It belongs to the i-declension group (like the feminine nouns noć or stvar) but is almost always used in the plural. Because the subject is plural, the verb krvariti (to bleed) must take the 3rd-person plural form krvare.

Why use the infinitive kupiti directly after morate instead of da kupite?

In standard Croatian, modal verbs like morati (to have to) are followed directly by the infinitive (kupiti). While you might hear da plus the present tense (morate da kupite) in some regional dialects or in Serbian, standard Croatian strongly prefers combining the modal directly with the infinitive.

Why does the sentence use četkicu instead of the base word četku?