Gregory R. Guy is Professor of Linguistics at New York University; his research focuses on social, geographic, and diachronic diversity in language, and the implications of linguistic variation for the construction of linguistic theory. He has done original research on variation and change in varieties of English, Spanish, and Portuguese, and on the African influences on language in Latin America. His current work addresses the coherence of lects, advancing cross-cultural sociolinguistics, and variation and change in the use of null subjects in Portuguese dialects. He previously held faculty positions at Sydney, Stanford, Cornell, and York (Canada), and has been a visiting professor or invited lecturer at universities in Brazil, Britain, Ireland, New Zealand, Germany, and the Netherlands. His publications include Towards a Social Science of Language (Benjamins, 1995, 1996), and Sociolingüística Quantitativa: Instrumental de Análise (Parábola, 2007). As a life-long activist for social diversity and human rights, he has served on professional, municipal, and national panels addressing issues of disability, inclusion, and accessibility in higher education and in the workplace, and on the promotion of linguistic human rights.