Learn Italian: Chi rompe qualcosa paga. - Whoever breaks something pays.

When chi is used outside of a question, it acts as a generalized relative pronoun meaning "whoever," "anyone who," or "the person who." It essentially absorbs both "the person" and "who" into a single word.

If chi can mean "the people who," why are the verbs rompe and paga in the singular?

Grammatically, chi is strictly a third-person singular pronoun. Even if you are referring to a group of people, any verb attached to chi must be conjugated in the singular. That is why we use rompe and paga rather than their plural forms.

There are two verbs here (rompe and paga) but only one subject. Is that correct?

Yes! Because chi means "the person who," it serves as the subject for both actions. It acts as the subject of the relative clause (rompe qualcosa) and also the subject of the main clause (paga). You do not need to add another pronoun before paga.

Is this a common saying in Italian?

Yes, this is a very common idiom. The full proverb is Chi rompe paga e i cocci sono suoi (Whoever breaks it pays, and the shattered pieces are theirs). It is used to say that you must take full responsibility for your own mistakes.