English verb conjugation
CAN TOUGHEN

Regular verb: toughen - toughened - toughened

Affirmation

Simple form	V-ing form
I can toughen you can toughen he can toughen we can toughen you can toughen they can toughen	I can be toughening you can be toughening he can be toughening we can be toughening you can be toughening they can be toughening
Perfect	V-ing perfect
I can have toughened you can have toughened he 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 he 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
I cannot toughen you cannot toughen he cannot toughen we cannot toughen you cannot toughen they cannot toughen	I cannot be toughening you cannot be toughening he cannot be toughening we cannot be toughening you cannot be toughening they cannot be toughening
Perfect	V-ing perfect
I cannot have toughened you cannot have toughened he 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 he 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
can I toughen? can you toughen? can he toughen? can we toughen? can you toughen? can they toughen?	can I be toughening? can you be toughening? can he be toughening? can we be toughening? can you be toughening? can they be toughening?
Perfect	V-ing perfect
can I have toughened? can you have toughened? can he 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 he 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
can I not toughen? can you not toughen? can he 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 he not be toughening? can we not be toughening? can you not be toughening? can they not be toughening?
Perfect	V-ing perfect
can I not have toughened? can you not have toughened? can he 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 he not have been toughening? can we not have been toughening? can you not have been toughening? can they not have been toughening?