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 cannot toughen
you cannot toughen
she cannot toughen
we cannot toughen
you cannot toughen
they cannot toughen 	I cannot be toughening
you cannot be toughening
she cannot be toughening
we cannot be toughening
you cannot be toughening
they cannot be toughening	I cannot have toughened
you cannot have toughened
she cannot have toughened
we cannot have toughened
you cannot have toughened
they cannot have toughened	I cannot have been toughening
you cannot have been toughening
she cannot have been toughening
we cannot have been toughening
you cannot have been toughening
they cannot 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 I not toughen?
can you not toughen?
can she not toughen?
can we not toughen?
can you not toughen?
can they not toughen? 	can I not be toughening?
can you not be toughening?
can she not be toughening?
can we not be toughening?
can you not be toughening?
can they not be toughening? 	can I not have toughened?
can you not have toughened?
can she not have toughened?
can we not have toughened?
can you not have toughened?
can they not have toughened? 	can I not have been toughening?
can you not have been toughening?
can she not have been toughening?
can we not have been toughening?
can you not have been toughening?
can they not have been toughening?