約

It is a phono-semantic compound, composed of:

糸 (silk, thread) – semantic element, indicating threads and binding;

勺 (jak, ladle) – phonetic element, giving sound.

Semantic range:

- to bind, to tie together – from the image of silk threads being bound.

- to promise, to make an agreement – by extension, to form a pact or arrangement (約束, 약속).

- approximately, about – as in estimation or rough agreement.

- to reduce (fractions) – a rarer meaning, seen in terms like 約數 (yak-su, divisor; reduced number).

In Korean, 약 (約) is extremely common in everyday and technical vocabulary:

약속 (約束) – promise, appointment

약간 (若干/約間) – a little, somewhat (approximate)

약수 (約數) – divisor (in math)

약분 (約分) – reduction (of fractions)

조약 (條約) – treaty

간약 (簡約) – concise, simple