union

The word "union" has a broad range of meanings, but they all center on the idea of things being joined or combined. At its most basic, a union is simply the act of coming together, like the joining of two rivers into one larger stream.

Often, "union" suggests something more deliberate and important than a simple connection. It can refer to a marriage or another close partnership: "Their union was blessed by family and friends." It can also describe a political joining or alliance: "The union between the two countries strengthened their economies."

In everyday modern use, "union" very often refers to a labor organization: a group of workers who join together to ask for better pay, safer working conditions, and benefits. These groups speak and negotiate for their members as one body. "She was an active member of the teachers' union."

The idea also extends beyond people. In mathematics, especially in set theory, a union is the set that contains all elements found in any of the sets being combined. The word can also be used more generally for any blending or joining of parts into a whole.

Historically, the word can refer to the joining of separate states or territories into one political whole. In U.S. history, "the Union" most famously meant the Northern states that remained loyal to the federal government during the American Civil War.

So whether it is about marriage, workers, politics, mathematics, or history, a union points to the same core idea: separate parts coming together to form one whole, often with a shared purpose.