could darken
Regular verb: darken - darkened- darkened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could darken
you could darken
she could darken
we could darken
you could darken
they could darken 	I could be darkening
you could be darkening
she could be darkening
we could be darkening
you could be darkening
they could be darkening	I could have darkened
you could have darkened
she could have darkened
we could have darkened
you could have darkened
they could have darkened	I could have been darkening
you could have been darkening
she could have been darkening
we could have been darkening
you could have been darkening
they could have been darkening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't darken
you couldn't darken
she couldn't darken
we couldn't darken
you couldn't darken
they couldn't darken 	I couldn't be darkening
you couldn't be darkening
she couldn't be darkening
we couldn't be darkening
you couldn't be darkening
they couldn't be darkening	I couldn't have darkened
you couldn't have darkened
she couldn't have darkened
we couldn't have darkened
you couldn't have darkened
they couldn't have darkened	I couldn't have been darkening
you couldn't have been darkening
she couldn't have been darkening
we couldn't have been darkening
you couldn't have been darkening
they couldn't have been darkening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I darken?
could you darken?
could she darken?
could we darken?
could you darken?
could they darken? 	could I be darkening?
could you be darkening?
could she be darkening?
could we be darkening?
could you be darkening?
could they be darkening? 	could I have darkened?
could you have darkened?
could she have darkened?
could we have darkened?
could you have darkened?
could they have darkened? 	could I have been darkening?
could you have been darkening?
could she have been darkening?
could we have been darkening?
could you have been darkening?
could they have been darkening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I darken?
couldn't you darken?
couldn't she darken?
couldn't we darken?
couldn't you darken?
couldn't they darken? 	couldn't I be darkening?
couldn't you be darkening?
couldn't she be darkening?
couldn't we be darkening?
couldn't you be darkening?
couldn't they be darkening? 	couldn't I have darkened?
couldn't you have darkened?
couldn't she have darkened?
couldn't we have darkened?
couldn't you have darkened?
couldn't they have darkened? 	couldn't I have been darkening?
couldn't you have been darkening?
couldn't she have been darkening?
couldn't we have been darkening?
couldn't you have been darkening?
couldn't they have been darkening?