It's Merriam-Webster's Word of the Day for July 4th.
Today's word is semi-quincentennial, spelled S-E-M-I-Q-U-I-N-C-E-N-T-E-N-N-I-A-L.
Semi-quincentennial is a noun.
It refers to a 250th anniversary or its celebration.
The word can also be used as an adjective to describe something related
to or associated with such an anniversary or its celebration, as in semi-quincentennial festivities.
Here's the word used in a sentence from USA Today.
July 4, 2026, marks the nation's semi-quincentennial,
its 250th birthday since the signing of the Declaration of Independence.
Everyone knows that if you stick a feather in your hat for, say, a Fourth of July celebration, it's called macaroni.
But what does a Yankee doodle dandy call the celebration itself,
specifically when it marks the 250th year since the nation's founding?
Such a special day calls for a special word,
and semi-quincentennial fits the bill, as it does for any anniversary of the same esteemed and venerable vintage.
If the word's mouthful of seven syllables overwhelms, it's simple to break down.
The prefix semi here means half in quantity or value,
while quincentennial refers to a whopping 500th anniversary or its celebration.
Quin comes from the Latin word quinque, meaning five,
and centennial comes in part from the Latin centum, meaning hundred.
Hence, a semi-quincentennial is celebrated precisely halfway en route to a quincentennial.