Brian P. Cleary explains with humor and rhyme what adjectives are in a way even very young children can understand. Beginning with a definition of the word adjective, he uses dozens of them in the book as examples. Here is a sentence from the book, “They tell if root beer’s flat or fizzy, and if your street is quiet or busy, that treats are yummy, shakes are thick, and if your tummy’s calm or sick.” Immediately children relate to the cartoon drawings and humorous writing. The adjectives throughout the book are identified with colors, while the rest of the text is black. Even if children cannot yet read, they could point to the colored words to realize adjectives are in sentences, and are special words.
My FREE PDF is one to fill out while on an adjective walk around the neighborhood or near the school (maybe even from the playground). Actually take the children outside and have them tell about the things they are seeing, and they will realize they already use describing words. Hairy, Scary, Ordinary: What is an Adjective? PDF
Here is another version for an adjective walk without the book.