Forensic textile science is a relatively young discipline; fibre identification is the most established component of this discipline. Textile products of interest to the forensic scientist include individual fibres, yarns, fabrics, apparel household textiles and furnishings and are hierarchical structures; fibres are used to manufacture yarns which are used to manufacture fabrics which are in turn used to manufacture products such as apparel, curtains, sheets, etc. Such products are often potential evidence in criminal investigations; typically supporting in nature. Of particular interest is damage caused to apparel during an alleged incident, fibre identification with respect to trace evidence and how blood interacts with fabrics. The correct and full description of a textile product using the appropriate discipline's terminology is critical and therefore this Chapter provides a brief introduction to textile science terminology.