The word 嘴巴 is formed by combining the character 嘴, which specifically means "mouth" or "beak", with the character 巴, which here functions not as an independent word but as a phonetic and semantic suffix. This 巴 adds a colloquial, concrete, and sometimes slightly informal nuance, turning the more standard term 嘴 into a word that often emphasizes the physical, fleshy part of the mouth (like the lips or the opening itself) commonly used in everyday speech. Its formation is an example of lexical compounding where the second element modifies and "grounds" the first, creating a single, integrated concept.