Present participle; Past participle - warning - warned Present - warn - warn - warns - warn - warn - warn Past - warned - warned - warned - warned - warned - warned Future - will warn - will warn - will warn - will warn - will warn - will warn Present conditional - would warn - would warn - would warn - would warn - would warn - would warn Present Perfect - have warned - have warned - has warned - have warned - have warned - have warned Past Perfect - had warned - had warned - had warned - had warned - had warned - had warned Future Perfect - will have warned - will have warned - will have warned - will have warned - will have warned - will have warned Past conditional - would have warned - would have warned - would have warned - would have warned - would have warned - would have warned Imperative - - - warn - - - - - - - -