This document discusses the pronunciation of the letters S, Z, and C in Catalan words. It explains that S can be either sonorous (like in "rosa") or voiceless (like in "sala") depending on its position in a word. Z is always pronounced like the sonorous S. The letters S, SS, Ç and C between vowels are voiceless. Examples are provided to demonstrate when each letter is sonorous or voiceless in pronunciation.