This article presents an overview of compounding in contemporary Portuguese. Conceived as a plurilexematic unit used as a holistic denomination, a compound is characterized by lexical atomicity. The continuum of compound classes that we propose is based on the morpho-lexical nature of the internal units (root, word) and on the (non)conformity of compound constructions with Portuguese syntactic templates. Since Portuguese compounds constitute a heterogeneous and borderline class, this analysis also focuses on the boundaries of compoundhood, namely those existing between compounds and noun phrases. This article also concentrates on the internal grammatical (coordinative, subordinative, attributive) and thematic relations and analyses Portuguese compounds with respect to headedness in its morphological, semantic and categorial dimensions. Finally, we stress the existence of a narrow relationship between internal constituency, headedness and inflectional patterns of Portuguese compounds.