This study offers a linguistic analysis of language borrowing in expertly produced paraphrases. Within the context of higher education, paraphrase writing, an essential skill for source-based writing tasks across the curriculum and a key component in the development of disciplinary expertise, represents a challenge for students and teachers because 1) there is no precise and generally accepted definition of acceptable academic paraphrase, 2) discussions of paraphrase are more often framed in terms of plagiarism than effective writing, and 3) little is known about the linguistic (or rhetorical dimensions) of paraphrases in writing published by experts. The present study analyzes five corpora of paraphrase/source passage pairs (n = 233) produced by expert writers. Corpora 1 and 2 contain exemplar paraphrase/source passage pairs drawn from writing guides and handbooks designed for college students. The remaining three corpora of paraphrase/source passage pairings were assembled using award-winning published articles in three disciplines. Using Keck’s (2006) taxonomy for classifying paraphrases, the study found that about 27% of the average paraphrase of the expert writers analyzed here is made up of language found in the source passage. Paraphrase patterns of expert academic writers point toward a potential continuum of acceptable language borrowing practices likely driven by disciplinary differences. Implications for writing development, writing pedagogy, plagiarism policy, and further research are discussed.This study offers a linguistic analysis of language borrowing in expertly produced paraphrases. Within the context of higher education, paraphrase writing, an essential skill for source-based writing tasks across the curriculum and a key component in the development of disciplinary expertise, represents a challenge for students and teachers because 1) there is no precise and generally accepted definition of acceptable academic paraphrase, 2) discussions of paraphrase are more often framed in terms of plagiarism than effective writing, and 3) little is known about the linguistic (or rhetorical dimensions) of paraphrases in writing published by experts. The present study analyzes five corpora of paraphrase/source passage pairs (n = 233) produced by expert writers. Corpora 1 and 2 contain exemplar paraphrase/source passage pairs drawn from writing guides and handbooks designed for college students. The remaining three corpora of paraphrase/source passage pairings were assembled using award-winning published articles in three disciplines. Using Keck’s (2006) taxonomy for classifying paraphrases, the study found that about 27% of the average paraphrase of the expert writers analyzed here is made up of language found in the source passage. Paraphrase patterns of expert academic writers point toward a potential continuum of acceptable language borrowing practices likely driven by disciplinary differences. Implications for writing development, writing pedagogy, plagiarism policy, and further research are discussed.