Flexibility in its generic term is a measure of how bendable a thing is. It connotes how easily changes can be made to an object.
In the software context, flexibility is the adaptability of a program to future modifications. It is a quality of a program, software or application that allows programmers to modify it when required.
Flexibility allows to modify codes without having to re-write them. If software applications were not flexible, making new and updated releases of them would be a herculean task.
