Kongruenzsatz
... German for congruence theorem (externer Link)
Congruence theorem as a word is not commonly used in English maths. In German the word Kongruenzsatz usually means one out of four axioms. Each axiom tells you what you need to know about a triangle in order to draw it with accurate sides, angles and areas. In German, the plural "Kongruenzsätze" is used rather than the singular.