孙子 (sūnzi) literally combines 孙 (sūn), meaning 'grandchild' or specifically 'grandson', and 子 (zi), a common suffix for male offspring or a respectful/neutral noun marker. As a compound, it primarily means 'grandson' — the son of one's own child. It is used in family contexts, formal documents, and everyday speech when referring to male descendants two generations younger.

The same characters also refer to Sun Tzu (c. 5th century BCE), the ancient Chinese military strategist and author of The Art of War. In this proper noun usage, 孙子 is always capitalized in English and treated as a fixed historical name — not a descriptive phrase. Context determines whether the word means 'grandson' or 'Sun Tzu'; tone, surrounding words, and subject matter (e.g., family talk vs. history class) make the distinction clear.