Children with expressive language disorder have difficulty conveying or expressing information in speech, writing, sign language or gesture. (For preschool children, the difficulty expressing themselves in writing is not evident, as they have not started formal education.)
Rectangles have longer sides than any type of square. Opposite sides of rectangles are of equal lengths. All sides of squares are of equal lengths. Rectangles have longer sides than any type of square. Opposite sides of rectangles are of equal lengths. All sides of squares are of equal lengths.
As such we can say that a square is a  type of rectangle which is a type of shape. We can therefore pass a  square into any function that expects a shape or rectangle object  because a square is covariant with both a rectangle and a shape.