
Regular verb: alter - altered - altered
Simple form | V-ing form | 
| I may alter you may alter she may alter we may alter you may alter they may alter  | I may be altering you may be altering she may be altering we may be altering you may be altering they may be altering  | 
Perfect | V-ing perfect | 
| I may have altered you may have altered she may have altered we may have altered you may have altered they may have altered  | I may have been altering you may have been altering she may have been altering we may have been altering you may have been altering they may have been altering  | 
Simple form | V-ing form | 
| I mayn't alter you mayn't alter she mayn't alter we mayn't alter you mayn't alter they mayn't alter  | I mayn't be altering you mayn't be altering she mayn't be altering we mayn't be altering you mayn't be altering they mayn't be altering  | 
Perfect | V-ing perfect | 
| I mayn't have altered you mayn't have altered she mayn't have altered we mayn't have altered you mayn't have altered they mayn't have altered  | I mayn't have been altering you mayn't have been altering she mayn't have been altering we mayn't have been altering you mayn't have been altering they mayn't have been altering  | 
Simple form | V-ing form | 
| may I alter? may you alter? may she alter? may we alter? may you alter? may they alter?  | may I be altering? may you be altering? may she be altering? may we be altering? may you be altering? may they be altering?  | 
Perfect | V-ing perfect | 
| may I have altered? may you have altered? may she have altered? may we have altered? may you have altered? may they have altered?  | may I have been altering? may you have been altering? may she have been altering? may we have been altering? may you have been altering? may they have been altering?  | 
Simple form | V-ing form | 
| mayn't I alter? mayn't you alter? mayn't she alter? mayn't we alter? mayn't you alter? mayn't they alter?  | mayn't I be altering? mayn't you be altering? mayn't she be altering? mayn't we be altering? mayn't you be altering? mayn't they be altering?  | 
Perfect | V-ing perfect | 
| mayn't I have altered? mayn't you have altered? mayn't she have altered? mayn't we have altered? mayn't you have altered? mayn't they have altered?  | mayn't I have been altering? mayn't you have been altering? mayn't she have been altering? mayn't we have been altering? mayn't you have been altering? mayn't they have been altering?  |