nouns
the condition of being folded inward or sheathed
the folding in of an outer layer so as to form a pocket in the surface
"the invagination of the blastula"
(psychology) an introverted disposition; concern with one's own thoughts and feelings
domain category
the science of mental life
is a type of (narrower)
an unsociable disposition; avoiding friendship or companionship
is an attribute of
directed inward; marked by interest in yourself or concerned with inner feelings