could collaborate
Regular verb: collaborate - collaborated- collaborated

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could collaborate
you could collaborate
she could collaborate
we could collaborate
you could collaborate
they could collaborate 	I could be collaborating
you could be collaborating
she could be collaborating
we could be collaborating
you could be collaborating
they could be collaborating	I could have collaborated
you could have collaborated
she could have collaborated
we could have collaborated
you could have collaborated
they could have collaborated	I could have been collaborating
you could have been collaborating
she could have been collaborating
we could have been collaborating
you could have been collaborating
they could have been collaborating	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't collaborate
you couldn't collaborate
she couldn't collaborate
we couldn't collaborate
you couldn't collaborate
they couldn't collaborate 	I couldn't be collaborating
you couldn't be collaborating
she couldn't be collaborating
we couldn't be collaborating
you couldn't be collaborating
they couldn't be collaborating	I couldn't have collaborated
you couldn't have collaborated
she couldn't have collaborated
we couldn't have collaborated
you couldn't have collaborated
they couldn't have collaborated	I couldn't have been collaborating
you couldn't have been collaborating
she couldn't have been collaborating
we couldn't have been collaborating
you couldn't have been collaborating
they couldn't have been collaborating	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I collaborate?
could you collaborate?
could she collaborate?
could we collaborate?
could you collaborate?
could they collaborate? 	could I be collaborating?
could you be collaborating?
could she be collaborating?
could we be collaborating?
could you be collaborating?
could they be collaborating? 	could I have collaborated?
could you have collaborated?
could she have collaborated?
could we have collaborated?
could you have collaborated?
could they have collaborated? 	could I have been collaborating?
could you have been collaborating?
could she have been collaborating?
could we have been collaborating?
could you have been collaborating?
could they have been collaborating? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I collaborate?
couldn't you collaborate?
couldn't she collaborate?
couldn't we collaborate?
couldn't you collaborate?
couldn't they collaborate? 	couldn't I be collaborating?
couldn't you be collaborating?
couldn't she be collaborating?
couldn't we be collaborating?
couldn't you be collaborating?
couldn't they be collaborating? 	couldn't I have collaborated?
couldn't you have collaborated?
couldn't she have collaborated?
couldn't we have collaborated?
couldn't you have collaborated?
couldn't they have collaborated? 	couldn't I have been collaborating?
couldn't you have been collaborating?
couldn't she have been collaborating?
couldn't we have been collaborating?
couldn't you have been collaborating?
couldn't they have been collaborating?