Justyna Olko is a Researcher and Professor at the University of Warsaw. Recipient of two European Research Council grants and a 2020 winner of the Falling Walls Science Breakthrough of the Year. Her notable publications include Insignia of Rank in the Nahua World (University Press of Colorado, 2014) and Revitalizing Endangered Languages (co-edited with Sallabank, CUP, 2021). John Sullivan is Professor Emeritus at Universidad Autónoma de Zacatecas, an Instructor at the University of Warsaw, and an Associate Instructor at the University of Utah. He co-founded in 2001 the Instituto de Docencia e Investigación Etnológica de Zacatecas. He was a Guggenheim fellow (2007). Robert Borges is a Research Engineer and a Researcher in the Department of Statistics at Uppsala University. In linguistics, he specializes in language contact and multilingualism, and as a research engineer, he works with large textual corpora and questions surrounding sustainability in empirical research.

• List of tables; List of figures; Conventions for formatting, citations and glossing; Acknowledgements; 1. Introduction; 2. The Nahua world across the centuries: culture, communities, economy and politics; 3. Theoretical framework and methodology; 4. Nahuatl and its speakers: a sociolinguistic history; 5. A complex continuum: the sociolinguistic ecologies of Nahua communities today; 6. Contact-driven changes in the Nahuatl Lexicon; 7. Phonological change and continuity in Nahuatl; 8. The assimilation of Spanish loan matter into the Nahuatl morphological system; 9. Typological change: convergence and system-altering transformations; 10. Language contact, change and socio-cultural evolution across space and time; Archival sources; Audio sources; References.

Justyna Olko is a Researcher and Professor at the University of Warsaw. Recipient of two European Research Council grants and a 2020 winner of the Falling Walls Science Breakthrough of the Year. Her notable publications include Insignia of Rank in the Nahua World (University Press of Colorado, 2014) and Revitalizing Endangered Languages (co-edited with Sallabank, CUP, 2021). John Sullivan is Professor Emeritus at Universidad Autónoma de Zacatecas, an Instructor at the University of Warsaw, and an Associate Instructor at the University of Utah. He co-founded in 2001 the Instituto de Docencia e Investigación Etnológica de Zacatecas. He was a Guggenheim fellow (2007). Robert Borges is a Research Engineer and a Researcher in the Department of Statistics at Uppsala University. In linguistics, he specializes in language contact and multilingualism, and as a research engineer, he works with large textual corpora and questions surrounding sustainability in empirical research.

• List of tables; List of figures; Conventions for formatting, citations and glossing; Acknowledgements; 1. Introduction; 2. The Nahua world across the centuries: culture, communities, economy and politics; 3. Theoretical framework and methodology; 4. Nahuatl and its speakers: a sociolinguistic history; 5. A complex continuum: the sociolinguistic ecologies of Nahua communities today; 6. Contact-driven changes in the Nahuatl Lexicon; 7. Phonological change and continuity in Nahuatl; 8. The assimilation of Spanish loan matter into the Nahuatl morphological system; 9. Typological change: convergence and system-altering transformations; 10. Language contact, change and socio-cultural evolution across space and time; Archival sources; Audio sources; References.