if something coal something else then that something is the sink of that something else
coal is rock. coal_field is unnatural_thing. coal is naturally_occurring_tangible_substance. using_beings_as_things is slavery. steam_ejector is tangible_thing. wood_coal is organic_matter. piece_of_paper is lighter_than_chunk_of_coal. coal is fuel. sink is tangible_thing. coal is organic_matter.