could yowl
Regular verb: yowl - yowled- yowled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could yowl
you could yowl
he could yowl
we could yowl
you could yowl
they could yowl 	I could be yowling
you could be yowling
he could be yowling
we could be yowling
you could be yowling
they could be yowling	I could have yowled
you could have yowled
he could have yowled
we could have yowled
you could have yowled
they could have yowled	I could have been yowling
you could have been yowling
he could have been yowling
we could have been yowling
you could have been yowling
they could have been yowling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't yowl
you couldn't yowl
he couldn't yowl
we couldn't yowl
you couldn't yowl
they couldn't yowl 	I couldn't be yowling
you couldn't be yowling
he couldn't be yowling
we couldn't be yowling
you couldn't be yowling
they couldn't be yowling	I couldn't have yowled
you couldn't have yowled
he couldn't have yowled
we couldn't have yowled
you couldn't have yowled
they couldn't have yowled	I couldn't have been yowling
you couldn't have been yowling
he couldn't have been yowling
we couldn't have been yowling
you couldn't have been yowling
they couldn't have been yowling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I yowl?
could you yowl?
could he yowl?
could we yowl?
could you yowl?
could they yowl? 	could I be yowling?
could you be yowling?
could he be yowling?
could we be yowling?
could you be yowling?
could they be yowling? 	could I have yowled?
could you have yowled?
could he have yowled?
could we have yowled?
could you have yowled?
could they have yowled? 	could I have been yowling?
could you have been yowling?
could he have been yowling?
could we have been yowling?
could you have been yowling?
could they have been yowling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I yowl?
couldn't you yowl?
couldn't he yowl?
couldn't we yowl?
couldn't you yowl?
couldn't they yowl? 	couldn't I be yowling?
couldn't you be yowling?
couldn't he be yowling?
couldn't we be yowling?
couldn't you be yowling?
couldn't they be yowling? 	couldn't I have yowled?
couldn't you have yowled?
couldn't he have yowled?
couldn't we have yowled?
couldn't you have yowled?
couldn't they have yowled? 	couldn't I have been yowling?
couldn't you have been yowling?
couldn't he have been yowling?
couldn't we have been yowling?
couldn't you have been yowling?
couldn't they have been yowling?