A collection is a group of objects that someone has gathered together, usually because they share something in common or hold special meaning. Someone might have a collection of rocks found on family vacations, stamps from different countries, or baseball cards organized by team and year. Museums display collections of paintings, fossils, or historical artifacts for the public to see and learn from.

What makes something a collection rather than just a pile of stuff? Collections are intentional and organized. A collector chooses what to include, arranges items carefully, and often keeps adding to the collection over time. Some collections become valuable: a collection of rare coins might be worth thousands of dollars. Others matter simply because they remind the collector of experiences and interests that shaped their life.

The word also means the act of gathering things together. When you do a collection of information for a research project, you're bringing facts and sources together in one place. Libraries have book collections, meaning all the books they've gathered and organized for people to use. A teacher might assign a collection of leaves to help students study different tree species.