Invagination refers to the process of folding or tucking one part of an anatomical structure inside another part, resulting in an inwardly directed pocket or fold. Synonyms for invagination include intussusception, infolding, introversion, or involution. These terms describe the same process of one part sliding inwardly into another, but may be used in specific contexts or for different anatomical structures. In medicine, intussusception is commonly used to describe the invagination of the bowel, whereas introversion may refer to the folding of the eyelid or uterus. Regardless of the terminology used, invagination is an important process in development and functioning of various tissues and organs in the body.