could lighten
Regular verb: lighten - lightened- lightened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could lighten
you could lighten
she could lighten
we could lighten
you could lighten
they could lighten 	I could be lightening
you could be lightening
she could be lightening
we could be lightening
you could be lightening
they could be lightening	I could have lightened
you could have lightened
she could have lightened
we could have lightened
you could have lightened
they could have lightened	I could have been lightening
you could have been lightening
she could have been lightening
we could have been lightening
you could have been lightening
they could have been lightening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't lighten
you couldn't lighten
she couldn't lighten
we couldn't lighten
you couldn't lighten
they couldn't lighten 	I couldn't be lightening
you couldn't be lightening
she couldn't be lightening
we couldn't be lightening
you couldn't be lightening
they couldn't be lightening	I couldn't have lightened
you couldn't have lightened
she couldn't have lightened
we couldn't have lightened
you couldn't have lightened
they couldn't have lightened	I couldn't have been lightening
you couldn't have been lightening
she couldn't have been lightening
we couldn't have been lightening
you couldn't have been lightening
they couldn't have been lightening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I lighten?
could you lighten?
could she lighten?
could we lighten?
could you lighten?
could they lighten? 	could I be lightening?
could you be lightening?
could she be lightening?
could we be lightening?
could you be lightening?
could they be lightening? 	could I have lightened?
could you have lightened?
could she have lightened?
could we have lightened?
could you have lightened?
could they have lightened? 	could I have been lightening?
could you have been lightening?
could she have been lightening?
could we have been lightening?
could you have been lightening?
could they have been lightening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I lighten?
couldn't you lighten?
couldn't she lighten?
couldn't we lighten?
couldn't you lighten?
couldn't they lighten? 	couldn't I be lightening?
couldn't you be lightening?
couldn't she be lightening?
couldn't we be lightening?
couldn't you be lightening?
couldn't they be lightening? 	couldn't I have lightened?
couldn't you have lightened?
couldn't she have lightened?
couldn't we have lightened?
couldn't you have lightened?
couldn't they have lightened? 	couldn't I have been lightening?
couldn't you have been lightening?
couldn't she have been lightening?
couldn't we have been lightening?
couldn't you have been lightening?
couldn't they have been lightening?