Present participle; Past participle - weakening - weakened Present - weaken - weaken - weakens - weaken - weaken - weaken Past - weakened - weakened - weakened - weakened - weakened - weakened Future - will weaken - will weaken - will weaken - will weaken - will weaken - will weaken Present conditional - would weaken - would weaken - would weaken - would weaken - would weaken - would weaken Present Perfect - have weakened - have weakened - has weakened - have weakened - have weakened - have weakened Past Perfect - had weakened - had weakened - had weakened - had weakened - had weakened - had weakened Future Perfect - will have weakened - will have weakened - will have weakened - will have weakened - will have weakened - will have weakened Past conditional - would have weakened - would have weakened - would have weakened - would have weakened - would have weakened - would have weakened Imperative - - - weaken - - - - - - - -