There are thousands of words in any language. But not all words have the same job. For example, some words express "action". Other words express a "thing". Other words "join" one word to another word. These are the "building blocks" of the language. Think of them like the Parts of a house. When we want to build a house, we use concrete to make the foundations or base. We use bricks to make the walls. We use window frames to make the windows, and door frames to make the doorways. And we use cement to join them all together. Each part of the house has its own job. And when we want to build a sentence, we use the different types of word. Each type of word has its own job.