Body part terms such as ​face can have various meanings, but the nature of those meanings varies across languages. Apart from its basic meaning ‘face’ as a human body part, the Vietnamese term m​ặt incorporates the notion of ‘surface’ and ‘frontside’ as well as specific metaphors for ‘sun’ and ‘moon’. This diversity of meanings poses a challenge for models of the structure of the mental lexicon. The approach adopted in this chapter suggests that body part extensions are established by a connection of similarity features between body parts and objects. In the case of the concept ​face​, these features include the function of ‘being a representation of an entity’, shape, and spatial alignment. The two similarity dimensions shape and spatial alignment seem to motivate a variety of semantic extensions and could provide valuable insights along with existing studies that investigate the cultural and physiological motivation of body part extension.