also key-note, "lowest note of a musical scale, basis of a scale," 1776, from key (n.1) in sense of "musical scale" + note (n.). Figurative sense of "leading idea" is from 1783; keynote address is 1905, American English.
权威例句
1. Choice is the keynote of the new education policy.
新教育政策的主导原则是容许选择。
2. The prime minister delivered the keynote address at the conference.
首相在会上作了基调演说.
3. Today the keynote of the wedding gown is simplicity.