Permissions are the atomic building block of access. In a subject-object-verb structure of access, permissions are the verb of access.
A resource is a fundamental part of the access vocabulary. In a subject-object-verb structure of access, a resource is the object being accessed.
A role is simply a collection of permissions. If a user assumes a role, they can take any of the actions associated with those permissions.
It makes sense to think of access in a subject-object-verb model.