The context in which medieval theologians discuss 'relation' is nearly always a trinitarian one. They have to solve an awkward problem: to explain how in God the persons are identical with the divine essence, yet different among themselves. In this paper I want to argue that Henry of Ghent's interest in the nature of the Trinity acted as an impetus towards the development of his theory of the nature of relations. In this context the accounts of Thomas Aquinas and Giles (...) of Rome will be considered as important for understand18 ing Henry's account. Henry's positive account of relations stems from Avicenna. For Henry, a relation is not an aliquid but has two modes of being, both as an accident and as a relative. Henry's attempt to think the nature of relation leads to him developing a relational ontology. (shrink)