誓

It is a phono-semantic compound, formed from:

言 (“speech, words”) as the semantic element;

折 (“to break, to bend”) as the phonetic element.

The image conveys the idea of binding words firmly, bending speech into a solemn promise.

Common compounds include:

맹서/맹세 (盟誓) – oath, vow

선서 (宣誓) – swearing in, taking an oath

충서 (忠誓) – vow of loyalty

Thus, 誓 carries the sense of a solemn promise expressed in words, and in Korean usage it survives both in formal/legal contexts (oaths, pledges) and in everyday expressions of vows.

The standard Sino-Korean reading is 서 (seo). However, in the compound 盟誓 (맹서/맹세), a glide assimilation phenomenon (활음조 현상) occurs, producing the variant pronunciation 세 (se).

Both 맹서 and 맹세 are officially recognized as standard Korean. According to the Korean Language Society (한국어문회):

맹서 (盟誓) is the original form.

맹세 is considered a colloquial/derived reading that became conventional over time.

Despite this, the character 誓 itself is not read as “세”; its correct Sino-Korean reading remains 서.

This means that while both “맹서” and “맹세” are accepted, when asked for the reading of the single character 誓, the proper answer is still “맹세할 서.”