could gnaw
Regular verb: gnaw - gnawed- gnawed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could gnaw
you could gnaw
she could gnaw
we could gnaw
you could gnaw
they could gnaw 	I could be gnawing
you could be gnawing
she could be gnawing
we could be gnawing
you could be gnawing
they could be gnawing	I could have gnawed
you could have gnawed
she could have gnawed
we could have gnawed
you could have gnawed
they could have gnawed	I could have been gnawing
you could have been gnawing
she could have been gnawing
we could have been gnawing
you could have been gnawing
they could have been gnawing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't gnaw
you couldn't gnaw
she couldn't gnaw
we couldn't gnaw
you couldn't gnaw
they couldn't gnaw 	I couldn't be gnawing
you couldn't be gnawing
she couldn't be gnawing
we couldn't be gnawing
you couldn't be gnawing
they couldn't be gnawing	I couldn't have gnawed
you couldn't have gnawed
she couldn't have gnawed
we couldn't have gnawed
you couldn't have gnawed
they couldn't have gnawed	I couldn't have been gnawing
you couldn't have been gnawing
she couldn't have been gnawing
we couldn't have been gnawing
you couldn't have been gnawing
they couldn't have been gnawing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I gnaw?
could you gnaw?
could she gnaw?
could we gnaw?
could you gnaw?
could they gnaw? 	could I be gnawing?
could you be gnawing?
could she be gnawing?
could we be gnawing?
could you be gnawing?
could they be gnawing? 	could I have gnawed?
could you have gnawed?
could she have gnawed?
could we have gnawed?
could you have gnawed?
could they have gnawed? 	could I have been gnawing?
could you have been gnawing?
could she have been gnawing?
could we have been gnawing?
could you have been gnawing?
could they have been gnawing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I gnaw?
couldn't you gnaw?
couldn't she gnaw?
couldn't we gnaw?
couldn't you gnaw?
couldn't they gnaw? 	couldn't I be gnawing?
couldn't you be gnawing?
couldn't she be gnawing?
couldn't we be gnawing?
couldn't you be gnawing?
couldn't they be gnawing? 	couldn't I have gnawed?
couldn't you have gnawed?
couldn't she have gnawed?
couldn't we have gnawed?
couldn't you have gnawed?
couldn't they have gnawed? 	couldn't I have been gnawing?
couldn't you have been gnawing?
couldn't she have been gnawing?
couldn't we have been gnawing?
couldn't you have been gnawing?
couldn't they have been gnawing?