Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could underlay sth you could underlay sth he could underlay sth we could underlay sth you could underlay sth they could underlay sth
V-ing form
I could be underlay sthing you could be underlay sthing he could be underlay sthing we could be underlay sthing you could be underlay sthing they could be underlay sthing
Perfect
I could have underlay sthed you could have underlay sthed he could have underlay sthed we could have underlay sthed you could have underlay sthed they could have underlay sthed
V-ing perfect
I could have been underlay sthing you could have been underlay sthing he could have been underlay sthing we could have been underlay sthing you could have been underlay sthing they could have been underlay sthing
Negation
Simple form
I couldn't underlay sth you couldn't underlay sth he couldn't underlay sth we couldn't underlay sth you couldn't underlay sth they couldn't underlay sth
V-ing form
I couldn't be underlay sthing you couldn't be underlay sthing he couldn't be underlay sthing we couldn't be underlay sthing you couldn't be underlay sthing they couldn't be underlay sthing
Perfect
I couldn't have underlay sthed you couldn't have underlay sthed he couldn't have underlay sthed we couldn't have underlay sthed you couldn't have underlay sthed they couldn't have underlay sthed
V-ing perfect
I couldn't have been underlay sthing you couldn't have been underlay sthing he couldn't have been underlay sthing we couldn't have been underlay sthing you couldn't have been underlay sthing they couldn't have been underlay sthing
Interrogative form
Simple form
could I underlay sth? could you underlay sth? could he underlay sth? could we underlay sth? could you underlay sth? could they underlay sth?
V-ing form
could I be underlay sthing? could you be underlay sthing? could he be underlay sthing? could we be underlay sthing? could you be underlay sthing? could they be underlay sthing?
Perfect
could I have underlay sthed? could you have underlay sthed? could he have underlay sthed? could we have underlay sthed? could you have underlay sthed? could they have underlay sthed?
V-ing perfect
could I have been underlay sthing? could you have been underlay sthing? could he have been underlay sthing? could we have been underlay sthing? could you have been underlay sthing? could they have been underlay sthing?
Interro-negative form
Simple form
couldn't I underlay sth? couldn't you underlay sth? couldn't he underlay sth? couldn't we underlay sth? couldn't you underlay sth? couldn't they underlay sth?
V-ing form
couldn't I be underlay sthing? couldn't you be underlay sthing? couldn't he be underlay sthing? couldn't we be underlay sthing? couldn't you be underlay sthing? couldn't they be underlay sthing?
Perfect
couldn't I have underlay sthed? couldn't you have underlay sthed? couldn't he have underlay sthed? couldn't we have underlay sthed? couldn't you have underlay sthed? couldn't they have underlay sthed?
V-ing perfect
couldn't I have been underlay sthing? couldn't you have been underlay sthing? couldn't he have been underlay sthing? couldn't we have been underlay sthing? couldn't you have been underlay sthing? couldn't they have been underlay sthing?