Functional completeness

Functional completeness means that a system or tool can do all the tasks it needs to do. Imagine you and your friends want to build a special treehouse for your childhood adventure. You would need a lot of different tools like saws, hammers, and nails to be able to make all the different parts of the treehouse. If you don't have all the tools, then you won't be able to finish the whole treehouse. This is the same with functional completeness - if a system doesn't have all the necessary tools or parts, then it won't be able to do all the tasks it needs to do.