The word "小朋友" is formed by combining two distinct concepts into a single, cohesive idea. It begins with "小" (xiǎo), meaning "small" or "little", which acts as a descriptive modifier. This is directly attached to "朋友" (péngyou), the core concept meaning "friend". The two parts are fused not grammatically, but semantically, to visually and conceptually create a new, unified notion: a "little friend", which is naturally understood to mean a child.