The kanji 約（やく） primarily conveys the idea of "promise," "agreement," "approximately," or "to reduce/shorten." It encompasses the concepts of binding oneself to something, making a deal, or simplifying something. It suggests a certain degree of approximation, limitation, or commitment.

・On-yomi (音読み): ヤク（yaku） ・Kun-yomi (訓読み): つづ-まる（tsuduma-ru）

⚫︎約束（やくそく） Translation: promise; agreement ⚫︎予約（よやく） Translation: reservation ⚫︎約10分（やくじゅっぷん） Translation: approximately 10 minutes

The kanji 約（やく） is a phono-semantic compound (形声文字, keisei moji). The left side is 糸（いと, ito - thread) which suggests the meaning of connection, binding, or tying something together. The right side is 勺（しゃく, shaku), which originally represented a ladle or a measuring tool. The combination suggests the idea of "tying together" or "measuring" something to a specific degree, thus leading to the meanings of "promise," "agreement," and "approximately." Over time, the meaning of measurement evolved to include "reduction" or "shortening," as in limiting something.