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