Present participle; Past participle - bittering - bittered Present - bitter - bitter - bitters - bitter - bitter - bitter Past - bittered - bittered - bittered - bittered - bittered - bittered Future - will bitter - will bitter - will bitter - will bitter - will bitter - will bitter Present conditional - would bitter - would bitter - would bitter - would bitter - would bitter - would bitter Present Perfect - have bittered - have bittered - has bittered - have bittered - have bittered - have bittered Past Perfect - had bittered - had bittered - had bittered - had bittered - had bittered - had bittered Future Perfect - will have bittered - will have bittered - will have bittered - will have bittered - will have bittered - will have bittered Past conditional - would have bittered - would have bittered - would have bittered - would have bittered - would have bittered - would have bittered Imperative - - - bitter - - - - - - - -