Present participle; Past participle - crumbling - crumbled Present - crumble - crumble - crumbles - crumble - crumble - crumble Past - crumbled - crumbled - crumbled - crumbled - crumbled - crumbled Future - will crumble - will crumble - will crumble - will crumble - will crumble - will crumble Present conditional - would crumble - would crumble - would crumble - would crumble - would crumble - would crumble Present Perfect - have crumbled - have crumbled - has crumbled - have crumbled - have crumbled - have crumbled Past Perfect - had crumbled - had crumbled - had crumbled - had crumbled - had crumbled - had crumbled Future Perfect - will have crumbled - will have crumbled - will have crumbled - will have crumbled - will have crumbled - will have crumbled Past conditional - would have crumbled - would have crumbled - would have crumbled - would have crumbled - would have crumbled - would have crumbled Imperative - - - crumble - - - - - - - -