could grass
Regular verb: grass - grassed- grassed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could grass
you could grass
she could grass
we could grass
you could grass
they could grass 	I could be grassing
you could be grassing
she could be grassing
we could be grassing
you could be grassing
they could be grassing	I could have grassed
you could have grassed
she could have grassed
we could have grassed
you could have grassed
they could have grassed	I could have been grassing
you could have been grassing
she could have been grassing
we could have been grassing
you could have been grassing
they could have been grassing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't grass
you couldn't grass
she couldn't grass
we couldn't grass
you couldn't grass
they couldn't grass 	I couldn't be grassing
you couldn't be grassing
she couldn't be grassing
we couldn't be grassing
you couldn't be grassing
they couldn't be grassing	I couldn't have grassed
you couldn't have grassed
she couldn't have grassed
we couldn't have grassed
you couldn't have grassed
they couldn't have grassed	I couldn't have been grassing
you couldn't have been grassing
she couldn't have been grassing
we couldn't have been grassing
you couldn't have been grassing
they couldn't have been grassing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I grass?
could you grass?
could she grass?
could we grass?
could you grass?
could they grass? 	could I be grassing?
could you be grassing?
could she be grassing?
could we be grassing?
could you be grassing?
could they be grassing? 	could I have grassed?
could you have grassed?
could she have grassed?
could we have grassed?
could you have grassed?
could they have grassed? 	could I have been grassing?
could you have been grassing?
could she have been grassing?
could we have been grassing?
could you have been grassing?
could they have been grassing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I grass?
couldn't you grass?
couldn't she grass?
couldn't we grass?
couldn't you grass?
couldn't they grass? 	couldn't I be grassing?
couldn't you be grassing?
couldn't she be grassing?
couldn't we be grassing?
couldn't you be grassing?
couldn't they be grassing? 	couldn't I have grassed?
couldn't you have grassed?
couldn't she have grassed?
couldn't we have grassed?
couldn't you have grassed?
couldn't they have grassed? 	couldn't I have been grassing?
couldn't you have been grassing?
couldn't she have been grassing?
couldn't we have been grassing?
couldn't you have been grassing?
couldn't they have been grassing?