friction

Everyday

1. Friction is a force that slows things down or stops them when two surfaces rub or slide against each other. tree →
2. Friction can mean disagreement or arguing between people. tree →

In the lessons

In science, friction acts against movement: rough surfaces like sandpaper and carpet make more friction, smooth or icy surfaces make less. Friction makes heat, which is why rubbing hands warms them. It is useful: shoe grips and bike brakes use friction to stop us slipping; but it also wears things out, so oil and wheels reduce it. In safety, ice and wet floors have little friction, so we slip. In everyday life, «friction between them» means they don't get on.

Examples

• Friction stops your shoes slipping on the floor. tree →
• Rub your hands together; friction makes them warm. tree →
• Ice has very little friction, so it's slippery. tree →
• Brakes use friction to slow a bike down. tree →
• The toy car went further on the smooth floor because there was less friction. tree →
• Oil reduces friction in machines. tree →
• There was some friction between the two teams. tree →

Note

Uncountable: «friction», not «a friction». Friction always pushes against the direction of movement. More friction = slower. Myth: friction is always bad — it is often useful (walking needs it). Air resistance and water resistance are kinds of friction.