Present participle; Past participle - summing - summed Present - sum - sum - sums - sum - sum - sum Past - summed - summed - summed - summed - summed - summed Future - will sum - will sum - will sum - will sum - will sum - will sum Present conditional - would sum - would sum - would sum - would sum - would sum - would sum Present Perfect - have summed - have summed - has summed - have summed - have summed - have summed Past Perfect - had summed - had summed - had summed - had summed - had summed - had summed Future Perfect - will have summed - will have summed - will have summed - will have summed - will have summed - will have summed Past conditional - would have summed - would have summed - would have summed - would have summed - would have summed - would have summed Imperative - - - sum - - - - - - - -