She was accepted to Harvard University for undergraduate education and received both her B.S. (Mathematics, 1970) and M.A./Ph.D. (Romance Languages, 1973). Her PhD dissertation was titled The Two Si's of Italian: An Analysis of Reflexive, Inchoative, and Indefinite Subject Sentences in Modern Standard Italian and was published by the Indiana University Linguistics Club.[5] A postdoctoral fellowship in linguistics at M.I.T. in 1974 led to her resulting career in the field.[6]
Napoli began her linguistics career in generative syntax, with a focus on Italian and other Romance languages. Her subsequent work spanned many topics within generative syntax on Romance languages and English, including its interfaces with intonation, morphology, and other areas.[7] She has worked in syntax, phonetics, phonology, morphology, historical and comparative linguistics, Romance studies, structure of American Sign Language, poetics, writing for ESL students, and mathematical and linguistic analysis of folk dance.
Her publications in linguistics include Syntactic argumentation (with Emily Rando). (Washington, DC: Georgetown Univ. Press, 1979), Syntax: Theory and Problems (Oxford: Oxford Univ. Press, 1993), Linguistics: An introduction (Oxford: Oxford Univ. Press, 1996), Humour in sign languages: The linguistic underpinnings (with Rachel Sutton-Spence) (Dublin: Trinity Press, 2009), and L'animale parlante ("The speaking animal") (2004), written with Marina Nespor,[8] along with dozens of articles in the scholarly journals.[9]
In 2015, she was inducted as a Fellow of the Linguistic Society of America.[10]