Present participle; Past participle - straightening - straightened Present - straighten - straighten - straightens - straighten - straighten - straighten Past - straightened - straightened - straightened - straightened - straightened - straightened Future - will straighten - will straighten - will straighten - will straighten - will straighten - will straighten Present conditional - would straighten - would straighten - would straighten - would straighten - would straighten - would straighten Present Perfect - have straightened - have straightened - has straightened - have straightened - have straightened - have straightened Past Perfect - had straightened - had straightened - had straightened - had straightened - had straightened - had straightened Future Perfect - will have straightened - will have straightened - will have straightened - will have straightened - will have straightened - will have straightened Past conditional - would have straightened - would have straightened - would have straightened - would have straightened - would have straightened - would have straightened Imperative - - - straighten - - - - - - - -