Any of the parts into which something is divided, or the act of creating these.

A person whose job is to supervise someone or something.

A ship that can travel underwater.

A railway system in which electric trains travel through tunnels below ground.

A large shop which sells most types of food and other goods needed in the home.

The act of watching a person or activity and making certain that everything is done correctly, safely, etc.

Having a lower or less important position.

To go below the surface of water.

Of the highest quality; the best.

An extremely famous actor, singer, musician, sports player, etc.

A person who is in charge of work done in a particular department, office, etc., or who is responsible for keeping a building or place in good condition.

Faster than the speed of sound.

To replace something, especially something older or more old-fashioned.

Used to refer to something less important than something else with which it is connected.

A set (= a group of similar numbers, objects, or people) that is part of another, larger set.

Better than average or better than other people or things of the same type.

A star that has exploded, strongly increasing its brightness for a few months.

To use something or someone instead of another thing or person.

The part of your mind that notices and remembers information when you are not actively trying to do so.