The noun 行星 (xíngxīng) means "planet," referring to a celestial body that orbits a star. In Chinese, 小行星 (xiǎo xíngxīng) means "asteroid," literally "small planet." This term appears frequently in scientific and astronomical contexts.
太阳系共有八大行星。
Tàiyángxì gòng yǒu bā dà xíngxīng.
There are a total of eight major planets in the solar system.
科学家发现了一颗新的行星。
Kēxuéjiā fāxiàn le yì kē xīn de xíngxīng.
Scientists have discovered a new planet.
火星是离地球最近的行星之一。
Huǒxīng shì lí Dìqiú zuì jìn de xíngxīng zhī yī.
Mars is one of the closest planets to Earth.