I'm looking for a technical name (if one exists) for a number that 'completes' or 'complements' another. The motivation for this is to develop a proper understanding of mathematical language, for example in naming variables while programming.
Say if I have a value x = 1/26. Is there a name for y = 25/26 that fills in the remaining part of the fraction?
In essence, if I have some x, I want a technical name for the value of y = (1-x).