睛 is almost exclusively used in 眼睛 (yǎnjīng, eye). Also appears in 目不转睛 (mùbùzhuǎnjīng, to stare without blinking) and 画龙点睛 (huàlóngdiǎnjīng, to add the finishing touch).
Left eye radical — pictograph of an eye, pupil and lid lines stacked vertically. 睛 specifically names the eyeball or pupil, the focused dark centre of vision. Always pairs with 眼 to make 眼睛, the everyday word for 'eyes' in modern Chinese.
Right 青 supplies the sound — qīng drifting to jīng via the q/j palatalisation, with the rest of the syllable kept. 青 means the clear blue-green of fresh growth. As phonetic in an eye-character it gives a faint semantic echo: the clear, bright iris — 火眼金睛.
