Modular means made up of separate, interchangeable parts that can be combined, rearranged, or replaced independently. Think of LEGO bricks: each piece is a module that connects to others in countless ways, and if one breaks, you can swap it out without rebuilding everything.

A modular bookshelf comes in separate sections you can stack or arrange however you want. As you get more books, you buy another module and add it on. Modular furniture is popular because it adapts to different spaces and needs instead of forcing you to work around one fixed design.

In technology, modular design makes things easier to fix and upgrade. A desktop computer is often modular: you can replace the graphics card or add more memory without replacing the entire machine. Video game designers create modular level pieces that they can arrange in different patterns, saving time while creating variety.

The opposite would be something built as one solid, unchangeable unit. A modular approach offers flexibility, letting you customize, expand, and repair things piece by piece. Scientists even talk about modular thinking, breaking complex problems into smaller, manageable parts that can be solved separately and then combined into a complete solution.