An assertion is a stylistic approach or technique involving a strong declaration, a forceful or confident, and a positive statement regarding a belief or a fact.

An assertion is often without proof or support. 

The purpose of assertion is to express ideas or feeling indirectly,

The function of assertion is to let readers feel they should not disagree or dispute what they read or hear.

Assertion has proven to be one of the best approaches for writers to  express their personal feelings, beliefs, and ideas directly.

When someone makes a statement investing his strong belief in it, as if it is true, though it may not be, he is making an assertion.

The behavior or attitude in response to something; an action in a reverse direction or manner is called reaction.

By using assertion in writing, writers can defend other’s feelings and rights if violated.

The purpose of assertion is to express unclear ideas or feeling directly.

Language assertion occurs when someone is not able to give a response to a person’s basic assertion and therefore that person becomes firm about him or her.