A thread is a long strand of material, often composed of several filaments or fibres, used for joining, creating or decorating textiles. Ancient Egyptians were known for creating thread using plant fibers, wool and hair. Today, thread can also be made of many different materials including but not limited to cotton, wool, flax, nylon, silk, polyester etc. There are also metal threads, which can be made of fine wire.

Yarn is a long continuous length of interlocked fibres, used in sewing, crocheting, knitting, weaving, embroidery, ropemaking, and the production of textiles. Thread is a type of yarn intended for sewing by hand or machine. Modern manufactured sewing threads may be finished with wax or other lubricants to withstand the stresses involved in sewing. Embroidery threads are yarns specifically designed for needlework. Yarn can be made of a number of natural or synthetic materials, and comes in a variety of colors and thicknesses. Although yarn may be dyed different colours, most yarns are solid coloured with a uniform hue.