Modular components are items that work together to form a single functioning item. In some cases, the modular piece may have a complete function that it is able to perform when not connected to any other piece, but this is uncommon. In most cases, a modular component is totally self-contained, but also dependent on other components to work. When multiple modular components are combined, they create a modular system. Since each part is separate, it is often possible to upgrade, change or repair one component while leaving the main system operational.
The cornerstone of modular components is the idea of self-containment. Everything that the component does is contained within the item itself. The component may need other parts to make its action useful, but they don’t directly influence the component. A car engine is a great example of this idea: it is complete and separate from the car, but without the rest of the parts, it doesn’t actually do anything when it runs.
This is where modular components differ from interchangeable components. Modular pieces are discrete parts of a system, such as a car engine. An interchangeable part is an item that has no function until it is placed with other items, like a belt within the engine. If a belt were sitting on the ground, it couldn’t actually perform a function without the engine, whereas the engine could still operate.
Another important factor in defining a modular component is in its function. A modular piece will typically perform a complex action, beyond what a single interchangeable part can do. Going back to the previous example, a fully functioning engine has far more uses than a single engine belt. Even if the two were used in places other than inside a car, the actions possible with the engine far outstrip any of its constituent parts.
This function is typically part of a larger picture. When modular components are by themselves, they are rarely useful. When those same components are connected, they will become greater than any one part individually. Each component is still separate and performing a single function, but when all those functions are combined, it creates a greater whole.
While most modular systems are interconnected, not all modular components need other pieces in order to work, such as in the case of modular furniture. While a modular desk may look strange by itself, it is still a desk and still works as well as any other desk. When other components, like an additional corner desk or hutch, are added to the system, the desk looks more correct and functions better.