IPA: /ˈstreɪtən/
KK: /ˈstreɪtən/
To make something that is not straight into a straight form.
She tried to straighten the picture frame on the wall.
Past: straightened
Past Participle: straightened
Straighten → It is formed from "straight" (from Old English *streht*, meaning extended or upright) and "-en" (a suffix used to form verbs indicating to cause to be or to become). The word "straighten" means to cause something to become straight or to make it upright.
Think of making something 'extended' or 'upright' — that's what it means to straighten something.