I. key ‧ note 1 /ˈkiːnəʊt $ -noʊt/ BrE AmE noun [countable]
the main point in a book, system of beliefs, activity etc that influences everything else
keynote of
Unprecedented change has been the keynote of the electronic revolution.
II. keynote 2 BrE AmE adjective [only before noun]
relating to the most important part of a formal meeting, report etc
keynote speech/address/lecture etc
He is scheduled to deliver the keynote address at an awards ceremony.
Bill Gates is booked as the keynote speaker.
III. keynote 3 BrE AmE verb [intransitive and transitive]
to give the keynote speech at a formal meeting, ceremony etc:
The event is usually keynoted by the prime minister.