This is the author accepted manuscript. The final version is available from Quodlibet via the DOI in this recordThe paper takes issue with Koslicki’s Neo-Aristotelian Mereology (NAM) and more particularly with her understanding of hylomorphism in mereological terms. NAM centres on two characteristic claims: (i) that Aristotle’s form is a proper part of the composite substance; (ii) that there is a univocal notion of part, and a univocal notion of composition, which apply across the board and to matter and form in particular. The paper shows that both assumptions are questionable within an Aristotelian framework. More in general, it is argued that a strictly mereological approach does not do justice to the complex relationship between matter...