A terminus is the end point of a transportation line, like the final stop on a train route or bus line. When a subway train reaches its terminus, it can't go any farther in that direction. Passengers must get off, and the train either turns around to head back or stops for the day. Grand Central Terminal in New York City is called a terminal because it's where many train lines end (even though the builders preferred the fancier Latin word “terminal” over “terminus”).

In ancient Rome, Terminus was the god of boundaries and landmarks, and Romans placed stones called termini to mark where one person's property ended and another's began.

Beyond transportation, terminus can describe the end point of anything: a river's terminus is where it flows into the ocean, and a glacier's terminus is its farthest edge. When scientists study glaciers, they measure how much the terminus has moved.

The plural can be either terminuses or termini (the Latin plural), though terminuses is more common in everyday speech.