首肯

Formal/written register, common in news reporting and corporate/official contexts. 首 here means 'head' (literal nodding); 肯 means 'to be willing/to consent'. Together: 'a nod of yes'. Distinct from everyday 同意 (agree) - 首肯 implies an authority granting permission from above.

memory

Picture a senior executive silently nodding (首) to give consent (肯) - that's exactly the image: approval given by a small, authoritative gesture rather than spoken words.