The two terms are not synonymous, but they are related. You use stretching as a method to improve flexibility. In reading the interview of strength coaches in the newest Training and Conditioning magazine it was interesting to read the responses to the question of flexibility. No doubt flexibility is an important component of athletic development. It is not a matter of stretching or not stretching or for that matter the type of stretching, for me it is when you strength to work on flexibility. One thing I know for sure that warm-up is not the place to work on flexibility. I know that from experience and it is substantiated by research.