binary mekso operator: mod(ulus)/remainder; X1 \% X2, \,\,\, X1 (mod(X2)).
Denoted as "\%" in C++. This is a basic arithmetic operator in some programming languages. x \% y is in [0, y) for all real numbers x and y, such that/where y > 0 definitionally, and outputs the modulus/remainder of its left-hand/first input (here: x) wrt/when integer-dividing it by its right-hand/second input (here: y); in other words, let n be the greatest integer such that n y =< abs(x), then this function yields abs(x) - n y. This function can also be used in order to define the fractional-part function (define y=1). See also: "vei'e".