could thicken
Regular verb: thicken - thickened- thickened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could thicken
you could thicken
she could thicken
we could thicken
you could thicken
they could thicken 	I could be thickening
you could be thickening
she could be thickening
we could be thickening
you could be thickening
they could be thickening	I could have thickened
you could have thickened
she could have thickened
we could have thickened
you could have thickened
they could have thickened	I could have been thickening
you could have been thickening
she could have been thickening
we could have been thickening
you could have been thickening
they could have been thickening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not thicken
you could not thicken
she could not thicken
we could not thicken
you could not thicken
they could not thicken 	I could not be thickening
you could not be thickening
she could not be thickening
we could not be thickening
you could not be thickening
they could not be thickening	I could not have thickened
you could not have thickened
she could not have thickened
we could not have thickened
you could not have thickened
they could not have thickened	I could not have been thickening
you could not have been thickening
she could not have been thickening
we could not have been thickening
you could not have been thickening
they could not have been thickening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I thicken?
could you thicken?
could she thicken?
could we thicken?
could you thicken?
could they thicken? 	could I be thickening?
could you be thickening?
could she be thickening?
could we be thickening?
could you be thickening?
could they be thickening? 	could I have thickened?
could you have thickened?
could she have thickened?
could we have thickened?
could you have thickened?
could they have thickened? 	could I have been thickening?
could you have been thickening?
could she have been thickening?
could we have been thickening?
could you have been thickening?
could they have been thickening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not thicken?
could you not thicken?
could she not thicken?
could we not thicken?
could you not thicken?
could they not thicken? 	could I not be thickening?
could you not be thickening?
could she not be thickening?
could we not be thickening?
could you not be thickening?
could they not be thickening? 	could I not have thickened?
could you not have thickened?
could she not have thickened?
could we not have thickened?
could you not have thickened?
could they not have thickened? 	could I not have been thickening?
could you not have been thickening?
could she not have been thickening?
could we not have been thickening?
could you not have been thickening?
could they not have been thickening?