Present participle; Past participle - lengthening - lengthened Present - lengthen - lengthen - lengthens - lengthen - lengthen - lengthen Past - lengthened - lengthened - lengthened - lengthened - lengthened - lengthened Future - will lengthen - will lengthen - will lengthen - will lengthen - will lengthen - will lengthen Present conditional - would lengthen - would lengthen - would lengthen - would lengthen - would lengthen - would lengthen Present Perfect - have lengthened - have lengthened - has lengthened - have lengthened - have lengthened - have lengthened Past Perfect - had lengthened - had lengthened - had lengthened - had lengthened - had lengthened - had lengthened Future Perfect - will have lengthened - will have lengthened - will have lengthened - will have lengthened - will have lengthened - will have lengthened Past conditional - would have lengthened - would have lengthened - would have lengthened - would have lengthened - would have lengthened - would have lengthened Imperative - - - lengthen - - - - - - - -