Thais wai when greeting or leaving. Along with a wai, Thais usually say 'sawasdee,' which means 'hello' in English. The wai tradition has been succeeded to the present generation since Sukhotai Period, approximately A.D. 1238). Wai can also be used in articulating apology or gratitude. For these purposes, a person who wais usually says, 'khor-thod' or 'khob-khun,' respectively.