行星 (xíngxīng): planet

Measure Word

一颗行星 kē

Literally 'moving star' -- because planets appear to move against the background of fixed stars.

Tàiyángxì yǒu bā kē xíngxīng.

The solar system has eight planets.

Dìqiú shì yī kē xíngxīng.

Earth is a planet.

memory

行星 = 'walking star.' The ancient Chinese noticed planets 'walk' across the sky, unlike fixed stars (恒星 héngxīng, 'permanent stars').

行 xíng

星 xīng