The word **外孙 (wàisūn)**, meaning "daughter's son" or "grandson (from the female line)," is formed through semantic compounding, combining the character **外 (wài)**, meaning "outside" or "external," with **孙 (sūn)**, meaning "grandchild." This structure reflects the traditional Chinese patrilineal kinship system, where **外** specifies that the grandchild is from the "external" or maternal side of the family (i.e., through one's daughter, who marries into another family), in contrast to **孙 (sūn)** alone, which typically implies a grandson from the paternal line (one's son's son).