Read the dictionary definition of straighten. All definitions for this word.
1. put (things or places) in order
1. Tidy up your room!
2. make straight or straighter
1. Straighten this post
2. straighten hair
3. make straight
4. straighten by unrolling
1. roll out the big map
5. get up from a sitting or slouching position
1. The students straightened when the teacher entered
6. straighten up or out; make straight