A list of three or more materials or items is called a series. Short, choppy sentences can be combined into one long, clear sentence with a series.
We use a comma (,) to separate the ideas and the word and is used before the last word in a series.
The summer sky is clear. The summer sky is blue. The summer sky is beautiful.
The summer sky is clear, blue, and beautiful.
Apples are red. Apples are green. Apples are delicious.
Apples are red, green, and delicious.
Trees are good homes for squirrels. They are for birds and racoons too.
Trees are good homes for squirrels, birds, and racoons.