填空
tián kòng · HSK 4
to fill in a blank
📝 填 (fill) + 空 (empty/blank) = fill the blank
填 means to fill or stuff; 空 means empty space or a blank. Together: fill an empty slot — either a job vacancy or a blank line on a form. The classic 填空题 is a fill-in-the-blank exam question.
填 — earth 土 + 真 (zhēn, phonetic)
填 is a semantic-phonetic compound. The 土 (earth) radical signals the meaning—filling in with soil—while 真 supplies the sound (originally close to 'tian'). The original sense was to stuff or pack a hole with earth, later broadened to filling in any gap, form, or blank.
空 — cave radical 穴 + 工 (phonetic)
Originally a phono-semantic compound: 穴 (cave, hole) gives the meaning of emptiness or hollow space, while 工 supplies the sound. The earliest sense was 'hole' or 'cavity,' which extended to 'empty,' 'sky,' and 'in vain.' The reading kòng (4th tone) specifically means 'free time' or 'vacancy.'