"If [a given structure] A has no relations it is termed an algebraic structure, or simply an algebra" -
Wolfgang Rautenberg, A Concise Introduction to Mathematical Logic, 3rd edition, page 42.
I didn't understand Rautenberg's definition. Elementary algebra has at least one relation: the equality (or identity) relation, signalized by the symbol "="
The equality relation is quintessential to linear algebra and algebraic equations, such as "x +5 = y"
As linear algebra and algebraic equations are written in a language whose meaning is given by a structure and an interpretation function, why are structures with no relations called algebras?