can darken
Regular verb: darken - darkened- darkened

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

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

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

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