In mathematics, what is the meaning of a triple bar, an equal sign with another bar above?

Question

What is the overall name for a branch of applied mathematics used to study behaviour in strategic situations, in which an individual's success in making choices depends on the choices of others?

Answer 1

The symbol is also used in philosophy (to show material equivalence, or to show that two statements can be freely substituted for each other without change of meaning), in biology (to show synonyms based on the same type specimen) and in application design (as an interface element, effectively a stylised menu item, or to show justified text).