could slacken
Regular verb: slacken - slackened- slackened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could slacken
you could slacken
she could slacken
we could slacken
you could slacken
they could slacken 	I could be slackening
you could be slackening
she could be slackening
we could be slackening
you could be slackening
they could be slackening	I could have slackened
you could have slackened
she could have slackened
we could have slackened
you could have slackened
they could have slackened	I could have been slackening
you could have been slackening
she could have been slackening
we could have been slackening
you could have been slackening
they could have been slackening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not slacken
you could not slacken
she could not slacken
we could not slacken
you could not slacken
they could not slacken 	I could not be slackening
you could not be slackening
she could not be slackening
we could not be slackening
you could not be slackening
they could not be slackening	I could not have slackened
you could not have slackened
she could not have slackened
we could not have slackened
you could not have slackened
they could not have slackened	I could not have been slackening
you could not have been slackening
she could not have been slackening
we could not have been slackening
you could not have been slackening
they could not have been slackening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I slacken?
could you slacken?
could she slacken?
could we slacken?
could you slacken?
could they slacken? 	could I be slackening?
could you be slackening?
could she be slackening?
could we be slackening?
could you be slackening?
could they be slackening? 	could I have slackened?
could you have slackened?
could she have slackened?
could we have slackened?
could you have slackened?
could they have slackened? 	could I have been slackening?
could you have been slackening?
could she have been slackening?
could we have been slackening?
could you have been slackening?
could they have been slackening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not slacken?
could you not slacken?
could she not slacken?
could we not slacken?
could you not slacken?
could they not slacken? 	could I not be slackening?
could you not be slackening?
could she not be slackening?
could we not be slackening?
could you not be slackening?
could they not be slackening? 	could I not have slackened?
could you not have slackened?
could she not have slackened?
could we not have slackened?
could you not have slackened?
could they not have slackened? 	could I not have been slackening?
could you not have been slackening?
could she not have been slackening?
could we not have been slackening?
could you not have been slackening?
could they not have been slackening?