English verb conjugation
CAN STIFF

Regular verb: stiff - stiffed - stiffed

Affirmation

Simple form	V-ing form
I can stiff you can stiff he can stiff we can stiff you can stiff they can stiff	I can be stiffing you can be stiffing he can be stiffing we can be stiffing you can be stiffing they can be stiffing
Perfect	V-ing perfect
I can have stiffed you can have stiffed he can have stiffed we can have stiffed you can have stiffed they can have stiffed	I can have been stiffing you can have been stiffing he can have been stiffing we can have been stiffing you can have been stiffing they can have been stiffing

Negation

Simple form	V-ing form
I can't stiff you can't stiff he can't stiff we can't stiff you can't stiff they can't stiff	I can't be stiffing you can't be stiffing he can't be stiffing we can't be stiffing you can't be stiffing they can't be stiffing
Perfect	V-ing perfect
I can't have stiffed you can't have stiffed he can't have stiffed we can't have stiffed you can't have stiffed they can't have stiffed	I can't have been stiffing you can't have been stiffing he can't have been stiffing we can't have been stiffing you can't have been stiffing they can't have been stiffing

Interrogative form

Simple form	V-ing form
can I stiff? can you stiff? can he stiff? can we stiff? can you stiff? can they stiff?	can I be stiffing? can you be stiffing? can he be stiffing? can we be stiffing? can you be stiffing? can they be stiffing?
Perfect	V-ing perfect
can I have stiffed? can you have stiffed? can he have stiffed? can we have stiffed? can you have stiffed? can they have stiffed?	can I have been stiffing? can you have been stiffing? can he have been stiffing? can we have been stiffing? can you have been stiffing? can they have been stiffing?

Interro-negative form

Simple form	V-ing form
can't I stiff? can't you stiff? can't he stiff? can't we stiff? can't you stiff? can't they stiff?	can't I be stiffing? can't you be stiffing? can't he be stiffing? can't we be stiffing? can't you be stiffing? can't they be stiffing?
Perfect	V-ing perfect
can't I have stiffed? can't you have stiffed? can't he have stiffed? can't we have stiffed? can't you have stiffed? can't they have stiffed?	can't I have been stiffing? can't you have been stiffing? can't he have been stiffing? can't we have been stiffing? can't you have been stiffing? can't they have been stiffing?