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 can't toughen you can't toughen he 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 he can't be toughening we can't be toughening you can't be toughening they can't be toughening
Perfect	V-ing perfect
I can't have toughened you can't have toughened he 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 he 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
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't I toughen? can't you toughen? can't he 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 he be toughening? can't we be toughening? can't you be toughening? can't they be toughening?
Perfect	V-ing perfect
can't I have toughened? can't you have toughened? can't he 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 he have been toughening? can't we have been toughening? can't you have been toughening? can't they have been toughening?