Coupling means joining or connecting two things together. When railroad workers couple train cars, they link them so they move as one unit. Engineers use couplings (metal connectors) to join pipes, allowing water or gas to flow between them. In machinery, a coupling connects two shafts so they spin together, like how a car’s engine transfers power to the wheels.

The word also appears in science and technology. In physics, coupling describes how strongly two systems affect each other. Think of two tuning forks sitting near each other: strike one and the other might start humming too because sound waves couple them together. Scientists study the coupling between ocean temperatures and weather patterns to understand how changes in one create changes in the other.

You might hear someone describe two ideas or events as coupled, meaning they’re linked or happen together. A teacher might say that hard work is coupled with good results. When things are coupled, what happens to one affects the other, just like how coupled train cars must travel in the same direction at the same speed.