# UML Class Diagram

A diagram of classes as boxes, with lines showing how they relate.

## What is **UML Class Diagram**?

A **UML class diagram** is a drawing of classes as boxes (name, properties, methods) with lines showing how they relate: inheritance, composition and so on. It helps plan code before writing it.

Level: Journeyman · [More OOP terms at this level](https://www.ask-codey.com/glossary/subjects/oop/journeyman)

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/uml-class-diagram