The world "ori" means folding, and kami (changes to gami) means paper. Origami is a traditional Japanese art of folding paper, which started in the 17th century AD at the latest and was well known outside of Japan in the mid-1900's. The best known origami is the Japanese paper crane. Washi is the traditional origami paper used in Japan. Apparently, no one really knows who invented origami. Traditional Japanese origami, which has been practiced since the Edo era (1603–1867), has often been less strict about these conventions, sometimes cutting the paper or using nonsquare shapes to start with. There is a lot of different types of origami; action origami, modular origami, wet-folding, pureland origami, origami tessellations, and kirigami.