As you show how language and literacy are connected, I think of them as a circle or bracelet, each facet connected or intertwined. Since a child's ability to understand and use spoken language allows those skills to permeate written expression and language too, I feel like they are strongly united. Since oral language allows kids to communicate, written expression or reading through literacy also connects, too.
As a junior high teacher, I see my kids who are readers definitely have better grammar and writing skills than those kids who do ...
This solution briefly correlates language and literacy.