Define and unnecessary pronoun and provide an example in a sentence.

An unnecessary pronoun is a pronoun that does not add to the understanding of the poem. 
An example is: My mother she grounded me for staying out too late. 
In this example, "she" is an unnecessary pronoun. The reader already understands that the subject is "my mother". The "she" is unnecessary because it just stands in place for the noun before it needs to be referenced.

This book is very good