When you use two adjectives in a row to describe a noun, be sure to place a comma between the two adjectives.
It’s a gray, rainy day.
I bought shiny, new car.
The rough, boisterous crowd filled the street.
Use a comma between two adjectives describing a noun.
It’s your turn. Place a comma in this sentence: I love looking at the big beautiful mountains. Did you figure it out? Good for you!