答应
dāyìng · HSK 2
promise
🤝 答 = answer + 应 = respond; answering 'yes' to a request
答 means to answer or reply; 应 means to respond or comply. Together, answering-and-responding to a request becomes 'agree' or 'promise'. The 应 here is read yìng (4th tone), the 'respond/consent' sense.
答 — bamboo radical 竹 + 合 (combine)
Originally written with the bamboo radical because answers were inscribed on bamboo slips. The phonetic 合 ('to join, match') gives both the sound and the sense of a reply 'matching' a question. Over time 答 came to mean 'answer' or 'respond' generally.
应 — 广 (shelter) + 心 (heart) + 隹 (bird)
Originally written 應, this character combined a phonetic component with 心 (heart) to suggest 'responding from the heart' or 'answering a call'. The simplified form 应 keeps the top portion. Over time it broadened from 'respond/answer' to also mean 'should' or 'ought to'.