
Irregular verb: understand - understood - understood
Simple form | V-ing form | 
| I could understand you could understand he could understand we could understand you could understand they could understand  | I could be understanding you could be understanding he could be understanding we could be understanding you could be understanding they could be understanding  | 
Perfect | V-ing perfect | 
| I could have understood you could have understood he could have understood we could have understood you could have understood they could have understood  | I could have been understanding you could have been understanding he could have been understanding we could have been understanding you could have been understanding they could have been understanding  | 
Simple form | V-ing form | 
| I couldn't understand you couldn't understand he couldn't understand we couldn't understand you couldn't understand they couldn't understand  | I couldn't be understanding you couldn't be understanding he couldn't be understanding we couldn't be understanding you couldn't be understanding they couldn't be understanding  | 
Perfect | V-ing perfect | 
| I couldn't have understood you couldn't have understood he couldn't have understood we couldn't have understood you couldn't have understood they couldn't have understood  | I couldn't have been understanding you couldn't have been understanding he couldn't have been understanding we couldn't have been understanding you couldn't have been understanding they couldn't have been understanding  | 
Simple form | V-ing form | 
| could I understand? could you understand? could he understand? could we understand? could you understand? could they understand?  | could I be understanding? could you be understanding? could he be understanding? could we be understanding? could you be understanding? could they be understanding?  | 
Perfect | V-ing perfect | 
| could I have understood? could you have understood? could he have understood? could we have understood? could you have understood? could they have understood?  | could I have been understanding? could you have been understanding? could he have been understanding? could we have been understanding? could you have been understanding? could they have been understanding?  | 
Simple form | V-ing form | 
| couldn't I understand? couldn't you understand? couldn't he understand? couldn't we understand? couldn't you understand? couldn't they understand?  | couldn't I be understanding? couldn't you be understanding? couldn't he be understanding? couldn't we be understanding? couldn't you be understanding? couldn't they be understanding?  | 
Perfect | V-ing perfect | 
| couldn't I have understood? couldn't you have understood? couldn't he have understood? couldn't we have understood? couldn't you have understood? couldn't they have understood?  | couldn't I have been understanding? couldn't you have been understanding? couldn't he have been understanding? couldn't we have been understanding? couldn't you have been understanding? couldn't they have been understanding?  |