≅ (U+2245), another combination of "≈" and "=", which is used to indicate isomorphism or sometimes congruence
Recapitulation theory, a scientific theory influential on but no longer accepted in its original form by both evolutionary and developmental biology, namely, that the congruence in form between the same embryonic developmental stages of different species is evidence that the embryos are repeating the evolutionary stages of their ancestral history
Zeller's congruence is an algorithm devised by Christian Zeller to calculate the day of the week for any Julian or Gregorian calendar date.