This chapter first provides an understanding of what plagiarism means, as a foundation on which the other chapters can build. It then tests whether it is possible to achieve a functional definition of plagiarism. As the canonical repository of definitions, dictionaries may seem to be a logical place to start the search. However, most dictionary definitions of plagiarism are rather shorter than those found in university policies, and this suggests that they are insufficient for academic purposes. A survey of plagiarism policies at Chinese universities found that they differed from their Anglophone counterparts in that they lacked explicit definitions, and shifted among several terms for plagiarism in a way which was potentially confusing for students. As Tadros (1993) has pointed out, academic writers have a binary choice to make between attributing something to a source or averring it themselves, and averral is the default condition, and what the reader assumes in the absence of attribution.