Ajahn (Thai: อาจารย์, RTGS: achan, IPA: [ʔāː.tɕāːn], also romanized ajaan, aajaan, ajarn, ajahn, acharn and achaan) is a Thai language term which translates as "professor" or "teacher." It is derived from the Pali word ācariya, and is a term of respect, similar in meaning to the Japanese sensei, and is used as a title of address for high-school and university teachers, and for Buddhist monks who have passed ten vassa. The term "ajahn" is customarily used to address forest tradition monks and the term Luang Por, "Venerable father" is customarily used to address city tradition monks in Thai Buddhism.