Monomania

mon-ō-mā′ni-a, n. madne confined to one subject, or to one faculty of the mind: an unreasonable interest in any particular thing.— n. Monomā′niac , one affected with monomania.— adjs. Monomā′niac , -al , affected with monomania. [Gr. monos , alone, mania , madne .]