keynote
noun [ C ] uk/ˈkiː.nəʊt/ us/ˈkiː.noʊt/
要旨，主题，基调
the most important or most emphasized part of something
This issue has become the keynote of the election campaign. 这一问题已成为竞选活动的主题。
a keynote address/speech/speaker (= an important talk/speaker at a formal meeting) 主要演说／发言／发言者