Present participle; Past participle - stifling - stifled Present - stifle - stifle - stifles - stifle - stifle - stifle Past - stifled - stifled - stifled - stifled - stifled - stifled Future - will stifle - will stifle - will stifle - will stifle - will stifle - will stifle Present conditional - would stifle - would stifle - would stifle - would stifle - would stifle - would stifle Present Perfect - have stifled - have stifled - has stifled - have stifled - have stifled - have stifled Past Perfect - had stifled - had stifled - had stifled - had stifled - had stifled - had stifled Future Perfect - will have stifled - will have stifled - will have stifled - will have stifled - will have stifled - will have stifled Past conditional - would have stifled - would have stifled - would have stifled - would have stifled - would have stifled - would have stifled Imperative - - - stifle - - - - - - - -