sisekord

Sisekord is a term used in Estonian-language texts to denote an inward fold or crease within a structure. It does not have a single, universally accepted definition, and its exact meaning depends on the disciplinary context. The form combines sis- meaning inside with kord meaning fold or crease, signaling an inward deformation.

In biology and medicine, sisekord is used informally to describe an inward folding of tissue or membranous layers, as a descriptive shorthand for invagination or infolding. In anatomy, more precise terms such as invagination or infolding are often preferred.

In geology and petrology, the word has appeared as a way to refer to interiorly folded layers and fabrics within rock sequences, though standard terminology such as intrafold or internal structure is typically used in technical writing.

In cultural and literary usage, sisekord can be employed metaphorically to indicate inward psychological turn or complexity, rather than a physical fold.

See also: folding, invagination, gyrification, pleat.