Both compressional and extensional forces act along convergent boundaries. A fundamental distinction is extensional vs intensional type theory. Fault bend folds occur in both extensional and thrust faulting. See also intensional versus extensional equality. Grabens are tectonic features that form under extensional stresses. Rollover anticlines are anticlines related to extensional normal faults. The classes of an ontology may be extensional or intensional in nature. A language is intensional if it contains intensional statements, and extensional otherwise. The Rhine Graben is a major extensional basin. Fault-block mountains often result from rifting, an indicator of extensional tectonics. These are examples of extensional and intensional definitions of sets, respectively. Strike-slip tectonics also occurs at lateral offsets in extensional and thrust fault systems. The study of extensional flows is called extensional rheology. The language has very little inflectional morphology but much derivational and extensional morphology. Satisfactory accounts of general semantics extensional devices can be found easily.