塞

The character’s structure evolved from the ancient form 𡫳, which combined:

宀 (roof radical) — indicating a building or enclosed space;

工 (craft, structure) and 廾 (hands) — suggesting the act of filling or constructing inside a dwelling.

Later, 土 (earth) was added beneath, emphasizing the meaning “to fill with earth, to close an opening.”

Thus, 塞 originally depicted a dwelling or passage being filled or blocked, yielding the meanings “to block,” “to close,” or “to fortify.”

Phono-semantic structure: semantic component 土 (earth) + phonetic component 𡫳, both closely linked in sense and sound.

In Shuowen Jiezi《說文解字》, Xu Shen glossed 塞 as to obstruct (隔) and 𡫳 as to fill (窒); later scholars such as Duan Yucai (段玉裁) distinguished them as separate but historically interchangeable.

堵塞 (dǔsè) — to block; congestion

塞車 (sāichē) — traffic jam

邊塞 (biānsài) — border fortress

塞外 (sàiwài) — beyond the frontier

要塞 (yàosài) — fortress; stronghold

塞 is a polyphonic character with two principal readings that carry distinct senses:

sāi (색) — “to block up,” “to fill,” “to plug,” “to obstruct.”

sài (새) — “frontier,” “border fortress,” “strategic pass.”

sè — rare; occurs in a few fixed idioms.

Thus, the same character may refer to both a physical obstruction (“to seal an opening”) and a strategic frontier zone (“border defense,” “fortress town”).