Compression means squeezing or pressing something into a smaller space. When you stuff a sleeping bag into its sack, you're using compression to make it fit. When you sit on an overfilled suitcase to close it, you're compressing your clothes.

The word appears in many contexts. In science, compression is one of the fundamental forces, like when you squeeze a spring or press down on a bike pump. The air inside gets compressed, taking up less space but pushing back harder. In medicine, compression bandages squeeze injured areas to reduce swelling.

In technology, compression means reducing the size of digital files. When you compress a photo on your computer, special software removes unnecessary information to make the file smaller without losing too much quality. This matters because smaller files download faster and take up less storage space. MP3 music files use compression to fit hours of songs on your phone.

Compression can also describe a shortened version of something longer. A teacher might ask you to write a compressed summary of a chapter, capturing the main ideas in fewer words.

The opposite of compression is expansion, when something spreads out or takes up more space.