proclamation
An official public announcement about something important.
A proclamation is an official public announcement, usually about something important. When a mayor issues a proclamation declaring next Tuesday “Community Service Day,” or when a president makes a proclamation about a national emergency, they're making their decision known to everyone in a formal, official way.
A proclamation is like officially shouting something for the whole community, state, or country to hear. In American history, one of the most famous proclamations was President Lincoln's Emancipation Proclamation of 1863, which declared that enslaved people in Confederate states were free.
Proclamations are different from everyday announcements. Your teacher might announce tomorrow's homework, but that's not a proclamation. A proclamation carries official authority and weight. When a governor issues a proclamation declaring a state of emergency before a hurricane, that announcement can have real legal power: it can free up emergency funds, activate the National Guard, and temporarily change certain laws.
You might also hear the word used more casually, like when someone makes a bold proclamation that they're going to win the spelling bee. In this sense, it means announcing something confidently and dramatically, even without official authority.