can toughen
Regular verb: toughen - toughened- toughened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can toughen
you can toughen
she can toughen
we can toughen
you can toughen
they can toughen 	I can be toughening
you can be toughening
she can be toughening
we can be toughening
you can be toughening
they can be toughening	I can have toughened
you can have toughened
she can have toughened
we can have toughened
you can have toughened
they can have toughened	I can have been toughening
you can have been toughening
she can have been toughening
we can have been toughening
you can have been toughening
they can have been toughening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can't toughen
you can't toughen
she can't toughen
we can't toughen
you can't toughen
they can't toughen 	I can't be toughening
you can't be toughening
she can't be toughening
we can't be toughening
you can't be toughening
they can't be toughening	I can't have toughened
you can't have toughened
she can't have toughened
we can't have toughened
you can't have toughened
they can't have toughened	I can't have been toughening
you can't have been toughening
she can't have been toughening
we can't have been toughening
you can't have been toughening
they can't have been toughening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I toughen?
can you toughen?
can she toughen?
can we toughen?
can you toughen?
can they toughen? 	can I be toughening?
can you be toughening?
can she be toughening?
can we be toughening?
can you be toughening?
can they be toughening? 	can I have toughened?
can you have toughened?
can she have toughened?
can we have toughened?
can you have toughened?
can they have toughened? 	can I have been toughening?
can you have been toughening?
can she have been toughening?
can we have been toughening?
can you have been toughening?
can they have been toughening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can't I toughen?
can't you toughen?
can't she toughen?
can't we toughen?
can't you toughen?
can't they toughen? 	can't I be toughening?
can't you be toughening?
can't she be toughening?
can't we be toughening?
can't you be toughening?
can't they be toughening? 	can't I have toughened?
can't you have toughened?
can't she have toughened?
can't we have toughened?
can't you have toughened?
can't they have toughened? 	can't I have been toughening?
can't you have been toughening?
can't she have been toughening?
can't we have been toughening?
can't you have been toughening?
can't they have been toughening?