In ancient Chinese, “shou (首) and “tou (頭)”, both of which were synonyms, referred to the human head. However, they were different from each other in the senses of the original, extended, and style meaning, respectively. The original meaning of “shou” refers to “head” with emphasis on the face, and “tou” refers specifically to “top of head”. In terms of the extended meaning, the most remarkable difference between “shou” and “tou” is that “shou” has the usage of verb while “tou” does not. “Tou” is grammaticalized as a suffix while “shou” is not. Therefore, we deduce the reason why “shou” and “tou” are not extended synchronously, and reach a conclusion that the core meanings of the two words are different. The core meanings confine the semantic changes of the synonym. In addition, the usage of verb of “shou” and the grammaticalization of “tou” have been explained at the core meaning level, respectively. As for the style meaning, “shou” is thought to be more elegant than “tou”.