An ama is an unmarried woman over the age of 20 or a woman who becomes a priestess after the period of Shamini (a female Buddhist novice), even though she has been married.
尼（あま）とは20歳以上の未婚、もしくは結婚経験があっても沙弥尼（しゃみに）の期間を経て出家した女性のこと。