There are at least two meanings on the word congruent in mathematics. Two geometric figures are said to be congruent if one can be transformed into the other by an isometry (Coxeter and Greitzer 1967, p. 80). This
relationship, called geometric congruence,
is written 
.
(Unfortunately, the symbol 
is also used to denote an isomorphism.)
A number 
is said to be congruent to 
modulo 
if 
(
divides 
).
