The distinction is the polymer origin of the filament yarn. Artificial filaments are regenerated from natural cellulose (viscose rayon, cupro, lyocell, acetate), while synthetic filaments are produced from petrochemical polymers (polyester, nylon, polypropylene). A fabric's classification depends on which type of filament predominates by weight.

Both acetate and viscose rayon are artificial filaments and fall within this heading. High-tenacity viscose rayon fabrics have their own dedicated subheading (540810), while acetate fabrics and other non-high-tenacity artificial filament fabrics are distributed across the 540821–540834 subheadings based on fiber content percentage and finishing state.