1. To pull something that is soft or elastic so that it becomes bigger and very tight. English = stretch.
2. Of clothing, to become bigger so that it no longer fits well because it has been pulled or washed incorrectly. English = stretch.
3. Of ideas, arguments, etc., to separate out two or more aspects in order to make a distinction or clarify the situation.
4. To give more details to a story or to make a thing that you are talking about bigger, better, or worse than it actually is. English = elaborate, exaggerate.
5. In mathematics (algebra and calculus), to rewrite a formula as an equivalent product based on the meaning of the symbols and rules about their arrangement in the original formula. English = expand.