Prelingual deafness refers to deafness that occurs before learning speech or language. Speech and language typically begin to develop very early with infants saying their first words by age one. Therefore, prelingual deafness is considered to occur before the age of one, where a baby is either born deaf (known as congenital deafness) or loses hearing before the age of one. This hearing loss may occur for a variety of reasons and impacts cognitive, social, and language development.