fancu gismu

x1 is a function/single-valued mapping from domain x2 to range x3 defined by expression/rule x4.

See also mekso, bridi.

In notes:

bridi
x1 (du'u) is a predicate relationship with relation x2 among arguments (sequence/set) x3.
mekso
x1 [quantifier/expression] is a mathematical expression interpreted under rules/convention x2.
fatkajyfancu
x1=fc1 is an inverse function from domain x2=fc2 to range x3=fc3 defined by original function x4=f4
nutko
x1 is the language/sublanguage that uses no apparent terbri/selbri distinction and is used by x2 to express ideas (not text) x3.
pirxo
x1 is the language/sublanguage that uses no apparent recursion rules and is used by x2 to express ideas (not text) x3.
funtiio
x1 (plural of ordered pairs) is an exhaustive set (possibly infinite) of inputs/outputs defining a unary function which yields result x3 when given input x2; x1(x2) = x3
integrale
x1 (number) is the integral (limit) of function x2