This contribution proposes to map the concepts of parliament and parliamentarianism by providing definitions of the words associated with them, by shaping a model for a given organisation’s parliamentary nature and by developing analytical aspects of the concept of parliamentarianism. Specifically, it argues that: 1. modern legislatures are characterised by the conjunction of fourteen distinct organisational features; 2. parliamentarianism is marked by a willingness to monopolise a remarkable diversity of political tasks through the original conjunction of in situ performances and legal instruments; 3. parliamentary assemblies possess an intrinsically democratic quality. Despite democrats’ numerous disillusionments relating to legislatures, the contribution supports the view that, be it from a liberal, participatory or deliberative perspective, legislatures are an essential component in assessing the democratic nature of a given political regime.