Synonyms for the term "innie nipple" include "retracted nipple," "inverted nipple," and "invaginated nipple." These terms refer to a common physical variation in which the nipple appears to be concave or flat rather than protruding. While some individuals with innie nipples may find them embarrassing or uncomfortable, this variation is perfectly normal and does not usually cause health problems. In more severe cases, medical treatment may be recommended to correct the shape of the nipple. However, many individuals with innie nipples choose to embrace their unique anatomy and may even find that it enhances their sexual experiences.