The paper offers a new approach of the concept of ontological category. The starting point is the claim that the "substance ontologies" are based on the acceptance of the Semantic Compositionality Principle which is shown to have unacceptable ontological implications. The paper delineates a new semantics based on the Principle of Sentential Contextuality (or Context Principle) and, in accordance with it, a new ontology. From this principle a new semantic category dubbed "prime state of affairs" ("pristate" for short) is derived and it is shown that on this basis it is possible to work out the fundamental and, in one sense, unique ontological category called "prime fact" ("prifact" for short).