Bimodal bilingualism is an individual or community's bilingual competency in at least one oral language and at least one sign language. A substantial number of bimodal bilinguals are Children of Deaf Adults or other hearing people who learn sign language for various reasons. Deaf people as a group have their own sign language and culture, but invariably live within a larger hearing culture with its own oral language. Thus, "most deaf people are bilingual to some extent in [an oral] language in some form". In discussions of multilingualism in the United States, bimodal bilingualism and bimodal bilinguals have often not been mentioned or even considered, in part because American Sign Language, the predominant sign language used in the U.S., only began to be acknowledged as a natural language