Trust is an attitude that an agent (the trustor) has toward an entity (the trustee), such that the trustor counts upon the trustee to act in a way that is beneficial w.r.t. to the trustor’s goals. The notion of trust is relevantly discussed both in information science and philosophy. Unfortunately, we still lack a satisfying account for this concept. The goal of this article is to contribute to filling this gap. First, we take issue with some central tenets shared by the main philosophical accounts, such as that there is just one relation of trust, that this relation has three argument places, and that trust is reliance plus some extra factor. Second, we provide a novel account of trust, also discussing different levels of trust. According to the account we put forth here, the logical form of trust sentences is expressed by a four-place relation. Further, we distinguish and characterize four kinds of trust relations and their connections. We also argue that trust and reliance are different phenomena. Third, on the basis of the proposed account, we extend the Reference Ontology of Trust (ROT). We call the new version of ROT that includes this extension “ROT 3.0”. Finally, we discuss the implications of the new ontological definitions in the applications we have done of the concept of trust in other works, also pointing out future applications made possible by these novel accounts of trust.