A distinct elongated structure, characteristically 10 nm in diameter, that occurs in the cytoplasm of higher eukaryotic cells. Intermediate filaments form a fibrous system, composed of chemically heterogeneous subunits and involved in mechanically integrating the various components of the cytoplasmic space. Intermediate filaments may be divided into five chemically distinct classes: keratin filaments of mammalian epithelial cells; desmin filaments found in cells of muscles of all types; vimentin filaments found in mesenchymal cells; neurofilaments of neurons; and glial filaments found in all types of glial cells (Gene Ontology).