Deafness is a condition wherein the ability to detect certain frequencies of sound is completely or partially impaired. When applied to humans, the term hearing impaired is rejected by the Deaf Culture movement, where the terms deaf and hard-of-hearing are preferred.
People with unilateral hearing impairment (single sided deafness/SSD) have impairment in only one ear. This can impair a person’s ability to localize sounds (e.g., determining where traffic is coming from) and distinguish sounds from background noise in noisy environments, such as an office or classroom.
The word deaf, with a small d, is used to describe anyone with a severe hearing problem, sometimes including those who are hard of hearing too. However, ‘Deaf,’ with a large D, specifically means those who have been deaf all of their lives or before they began to learn to talk. This is known as being pre-lingually deaf. The distinction is that for Deaf people sign-language is their primary language while spoken languages like English are secondary. This means that understanding complicated messages in English can be more difficult for them.
See our blog on How to improve your communication with deaf and Deaf people