"English is not my first language," writes Nakia Smith on her TikTok account, although the 22-year-old grew up in Texas. The young African-American woman has been deaf since birth, and uses her large following on the social media app to promote her little-known dialect: Black American Sign Language. In her video clips, she tells her 400,000 followers about the differences between her language and the standard American Sign Language (ASL).