An intrinsic property is a property that a thing has itself, including its context. An extrinsic (or relational) property is a property that depends on a thing's relationship with other things. For example, mass is an intrinsic property of any physical object, whereas weight is an extrinsic property that varies depending on the strength of the gravitational field in which the respective object is placed. The question of intrinsicality and extrinsicality in empirically observable objects is a significant field of study in ontology, the branch of philosophy concerned with explaining the fundamental nature of being.