Hard of hearing is the term used to describe those who have a hearing loss, usually acquired post-lingually and whose communication mode is usually by speech. This term also covers those people who have become deafened later in their life.
A hearing impairment (HI) is a full or partial decrease in the ability to understand sounds. The term “hearing impaired” is often used to refer to those who are deaf but it is viewed negatively by members of the Deaf community who prefer the terms “Deaf” and “hard of hearing”. The “hearing impaired” term is incorrectly intended to cover Deaf and hard of hearing individuals under a single category. Deaf and hard of hearing persons in many countries reject this definition because it fails to recognise any distinction between these two groups. Deaf Australia uses the “hard of hearing” term in this case. SOURCE: Deaf Australia or found here