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