Read the book Blue Sea by Robert Kalan.
Early Literacy Aside--Example: Blue Sea uses the concept of size. You can build your child's vocabulary by talking about different words related to size, like big, bigger, biggest which compare sizes. Also offer words like huge, gigantic, humongous.
Early Literacy Aside--Empower: There are many opportunities throughout the day where you can add new words related to size, such as thin, fat, hard, soft, etc. Exposing your children to new words builds their vocabulary which will help them later understand what they read.