A "hypothetical world" refers to an imaginary or made-up situation or place that is not real but is used to explore possibilities and ideas. Full definition
By the power of constructive thought, the scientist creates hypothetical worlds which he then tests by means of observations and experiments. (religion-online.org)
Since January, scientists have been chasing Planet Nine: a distant hypothetical world that could have 10 times the mass of Earth and explain the peculiarly clustered orbits of six icy bodies beyond Neptune. (sciencemag.org)
But besides that, let's pretend we live in a hypothetical world where Embiid was healthy day one and drafted by the Sixers... would that really be that bad? (sbnation.com)