ASL
American Sign Language — the primary sign language of Deaf communities in the US and parts of Canada, distinct from English in grammar and vocabulary.
ASL is a fully formed natural language, not a translation of English. It has its own grammar, syntax, and idiomatic expressions. Many Deaf individuals use ASL as their first language and English as their second.
For live events, ASL interpretation serves the audience whose primary language is sign — a population that overlaps with but is distinct from the audience served by captions. Best practice for major public events is to provide both ASL interpretation and captions, since each serves a different segment of the broader Deaf and Hard of Hearing community.
WCAG 2.2 includes a Level AAA criterion (1.2.6 Sign Language, Prerecorded) but doesn't require sign language interpretation at AA conformance. Most ADA-aligned event programs treat ASL as a complement to captions for high-stakes public sessions.