The word "肿胀" is formed by combining two characters, both featuring the radical "⺼" (flesh), which semantically ties them to the body. The character "肿" incorporates "中" primarily for its phonetic value, while "胀" uses "长" for both phonetic approximation and semantic suggestion of growth. Together, these characters create a compound where each contributes the meaning of swelling, resulting in a term that denotes physical enlargement or edema.