keynote
/ˈkiːnəʊt ˈकीनोट्/ noun [C] 1 (usually sing.)] the central idea of a book, a speech, etc. (पुस्तक, भाषण आदि का) मुख्य विचार किसी सभा या उसके विषय का परिचय देने वाला अत्यंत महत्वपूर्ण वक्ता या भाषण
This particular issue is the keynote of the election campaign this year.
a keynote speech/speaker [a very important one, introducing a meeting or its subject]