It all has to do with perspectives of both Hearing and Deaf worlds, then it's how you view yourself. In the Hearing perspective, everything is based on the scale of Hearing, so unless you are stone-deaf and hear nada,you are not deaf at all, but maybe hard of hearing. You are only considered Deaf if you are born to parents who are Deaf and have grown up only knowing sign language as your first language. If you are in that category, then you become alienated by them because they cannot relate to you.
In the Deaf world, however, everything is based on deafness. Note, I didn't say scale of deafness here. It is more culture-based, because everyone ranging from mild to profound can identify in common experiences and perspectives of society around them. There is a gravity toward people who are just like themselves and understand each other in what they face in the world. There is pride in a common identity. The more you understand this identity, the more Deaf you become.