Hip-hop or hip hop music, also known as rap, and formerly as disco rap, is a genre of popular music that originated in the early 1970s by African Americans and Caribbean immigrants in the Bronx, a borough of New York City. Hip-hop music originated as an anti-drug and anti-violence genre consisting of stylized rhythmic music that often accompanies rapping, a rhythmic delivery of poetic speech. In the early 1990s, a professor of African American studies at Temple University said, "hip hop is something that blacks can unequivocally claim as their own." By the 21st century, the field of rappers had diversified racially and genderly. The music developed as part of the broader hip hop culture, a subculture defined by four key stylistic elements: MCing/rapping, DJing/scratching with turntables, breakdancing, and graffiti art. While often used to refer solely to rapping and rap music, "hip hop" more properly denotes the practice of the entire subculture. The term hip hop music is sometimes used synonymously with the term rap music, though rapping is not a required component of hip hop music; the genre may also incorporate other elements of the culture, including DJing, turntablism, scratching, beatboxing, and instrumental tracks.