keynote
n. countable B2 Upper Intermediate US //ˈkiˌnoʊt// UK //kˈiːnəʊt// key·note
n. the main idea or central theme of a speech, book, or meeting. It is also the name for the most important speech at a big event.
n. the central theme or primary principle of a discourse, policy, or event. In a musical context, it refers to the note on which a key or system of tones is based.
The keynote of the conference was innovation in technology.
The CEO delivered a powerful keynote that outlined the company's vision for the next decade.
The speaker's emphasis on environmental sustainability provided the keynote for the entire summit, influencing every subsequent panel discussion and workshop.
From key + note.
Usage
Often used as a modifier before another noun, such as 'keynote speaker' or 'keynote address'.