could grin
Regular verb: grin - grinned- grinned

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could grin
you could grin
she could grin
we could grin
you could grin
they could grin 	I could be grinning
you could be grinning
she could be grinning
we could be grinning
you could be grinning
they could be grinning	I could have grinned
you could have grinned
she could have grinned
we could have grinned
you could have grinned
they could have grinned	I could have been grinning
you could have been grinning
she could have been grinning
we could have been grinning
you could have been grinning
they could have been grinning	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't grin
you couldn't grin
she couldn't grin
we couldn't grin
you couldn't grin
they couldn't grin 	I couldn't be grinning
you couldn't be grinning
she couldn't be grinning
we couldn't be grinning
you couldn't be grinning
they couldn't be grinning	I couldn't have grinned
you couldn't have grinned
she couldn't have grinned
we couldn't have grinned
you couldn't have grinned
they couldn't have grinned	I couldn't have been grinning
you couldn't have been grinning
she couldn't have been grinning
we couldn't have been grinning
you couldn't have been grinning
they couldn't have been grinning	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I grin?
could you grin?
could she grin?
could we grin?
could you grin?
could they grin? 	could I be grinning?
could you be grinning?
could she be grinning?
could we be grinning?
could you be grinning?
could they be grinning? 	could I have grinned?
could you have grinned?
could she have grinned?
could we have grinned?
could you have grinned?
could they have grinned? 	could I have been grinning?
could you have been grinning?
could she have been grinning?
could we have been grinning?
could you have been grinning?
could they have been grinning? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I grin?
couldn't you grin?
couldn't she grin?
couldn't we grin?
couldn't you grin?
couldn't they grin? 	couldn't I be grinning?
couldn't you be grinning?
couldn't she be grinning?
couldn't we be grinning?
couldn't you be grinning?
couldn't they be grinning? 	couldn't I have grinned?
couldn't you have grinned?
couldn't she have grinned?
couldn't we have grinned?
couldn't you have grinned?
couldn't they have grinned? 	couldn't I have been grinning?
couldn't you have been grinning?
couldn't she have been grinning?
couldn't we have been grinning?
couldn't you have been grinning?
couldn't they have been grinning?