The word "后面" is formed by combining two conceptual components: "后", which conveys the fundamental idea of "rear" or "behind" in terms of sequence or position, and "面", which means "face" or "surface" and here extends to signify a specific "side" or "aspect". Together, they create a composite idea where "面" specifies that the "rear" is being referred to as a particular facing direction or locative plane, thus forming the complete spatial concept of "the back side" or "the area behind".