In a Nutshell: 恒星 (héngxīng) is the precise, scientific term for a “star.” The key concept is permanence, captured by the character
恒 (héng), meaning “constant” or “permanent.” This comes from the ancient observation that stars remain in fixed positions relative to one another in the night sky, unlike planets, which appear to wander. While the word
星星 (xīngxing) is a more general and common term for any bright dot in the sky,
恒星 is used when you need to be scientifically accurate.