A creole language, or simply a creole, is a stable language that originates seemingly as a nativized pidgin. This understanding of creole genesis culminated in Hall's notion of the pidgin-creole life cycle. While it is understood that creoles have certain grammatical similarities to each other and, arguably, not languages that they are derived from, no theory for explaining creole phenomena has been universally accepted. The relationship between pidgins and creoles and their similarities means that the distinction is not clear-cut and the variety of phenomena that arise to create pidgins and creoles are not understood very well. Likewise, efforts to articulate grammatical features (or sets of features) that are exclusive to creoles have been unsuccessful thus far.