Present participle; Past participle - concerning - concerned Present - concern - concern - concerns - concern - concern - concern Past - concerned - concerned - concerned - concerned - concerned - concerned Future - will concern - will concern - will concern - will concern - will concern - will concern Present conditional - would concern - would concern - would concern - would concern - would concern - would concern Present Perfect - have concerned - have concerned - has concerned - have concerned - have concerned - have concerned Past Perfect - had concerned - had concerned - had concerned - had concerned - had concerned - had concerned Future Perfect - will have concerned - will have concerned - will have concerned - will have concerned - will have concerned - will have concerned Past conditional - would have concerned - would have concerned - would have concerned - would have concerned - would have concerned - would have concerned Imperative - - - concern - - - - - - - -