could harden
Regular verb: harden - hardened- hardened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could harden
you could harden
he could harden
we could harden
you could harden
they could harden 	I could be hardening
you could be hardening
he could be hardening
we could be hardening
you could be hardening
they could be hardening	I could have hardened
you could have hardened
he could have hardened
we could have hardened
you could have hardened
they could have hardened	I could have been hardening
you could have been hardening
he could have been hardening
we could have been hardening
you could have been hardening
they could have been hardening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not harden
you could not harden
he could not harden
we could not harden
you could not harden
they could not harden 	I could not be hardening
you could not be hardening
he could not be hardening
we could not be hardening
you could not be hardening
they could not be hardening	I could not have hardened
you could not have hardened
he could not have hardened
we could not have hardened
you could not have hardened
they could not have hardened	I could not have been hardening
you could not have been hardening
he could not have been hardening
we could not have been hardening
you could not have been hardening
they could not have been hardening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I harden?
could you harden?
could he harden?
could we harden?
could you harden?
could they harden? 	could I be hardening?
could you be hardening?
could he be hardening?
could we be hardening?
could you be hardening?
could they be hardening? 	could I have hardened?
could you have hardened?
could he have hardened?
could we have hardened?
could you have hardened?
could they have hardened? 	could I have been hardening?
could you have been hardening?
could he have been hardening?
could we have been hardening?
could you have been hardening?
could they have been hardening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not harden?
could you not harden?
could he not harden?
could we not harden?
could you not harden?
could they not harden? 	could I not be hardening?
could you not be hardening?
could he not be hardening?
could we not be hardening?
could you not be hardening?
could they not be hardening? 	could I not have hardened?
could you not have hardened?
could he not have hardened?
could we not have hardened?
could you not have hardened?
could they not have hardened? 	could I not have been hardening?
could you not have been hardening?
could he not have been hardening?
could we not have been hardening?
could you not have been hardening?
could they not have been hardening?