Invaginating

Part of speech: verb

Definitions

1. The action describes the inward folding of a structure that results in a pocket or cavity being formed within it
2. This term refers to the biological mechanism where tissues or membranes fold back upon themselves to create an enclosed space
3. The process in which a surface bends inward causing a hollow or pocket to develop within it

Etymology: "Invaginating" is the present participle of "invaginate", which comes from Medieval Latin "invāgīnātus", the past participle of "invāgīnāre". That verb is built from the prefix "in-" ("into") and "vāgīna", the Latin word for "sheath". The image is literal: something is pushed into a sheath-like covering, so that one part folds into another and leaves a pocket behind. The sheath sense is the original one. Latin "vāgīna" referred to a scabbard for a sword or a covering around a plant stalk, and the same root gave English "vagina", which is a Latin anatomical borrowing meaning "sheath". "Invaginate" applies the same idea to tissue: a layer of an organ or membrane turns inward on itself, as in the folding of an embryo or the wall of the intestine. In that usage the word describes a fold that forms a hollow, rather than a sheath placed over a blade.