Dyers woad, scientifically known as Isatis tinctoria, is a plant species that belongs to the mustard family. It is a popular source of blue dye, and is commonly used in textiles and cosmetics. There are a few synonyms for dyers woad, including woad, pastel, and glastum. The term woad is particularly well-known due to its extensive use in ancient times, when it was used to produce blue body paint and tattoos. Meanwhile, pastel refers to the dried leaves of the plant, while glastum is an old Latin term that was used to describe the dye produced by dyers woad. Regardless of the term used, dyers woad remains a useful and valuable plant species to this day.