On the Definition of Word is a 1987 book by Anna Maria Di Sciullo and Edwin S. Williams in which the authors examine the notion of word in linguistics.

They distinguish four concepts of "word": listemes, morphological objects, syntactic atoms, and phonological words.

The authors' main claim is that there is a strict distinction between syntax and morphology.

Andrew Carstairs, Mark Baker, Sofia Ananiadou and Masayuki Ike-uchi have reviewed the book.

This article about a book on language, linguistics or translation is a stub.