The word "孙女" is formed by combining two characters: "孙", which originally denotes a grandchild or descendant in a familial line, and "女", which means female. When these characters are joined, "孙" provides the foundational meaning of a grandchild relationship, while "女" specifies the gender, resulting in a compound that precisely refers to a son's daughter, or granddaughter. This formation relies on the semantic contribution of each part to create a clear and specific familial term.