could prewarn
Regular verb: prewarn - prewarned- prewarned

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could prewarn
you could prewarn
he could prewarn
we could prewarn
you could prewarn
they could prewarn 	I could be prewarning
you could be prewarning
he could be prewarning
we could be prewarning
you could be prewarning
they could be prewarning	I could have prewarned
you could have prewarned
he could have prewarned
we could have prewarned
you could have prewarned
they could have prewarned	I could have been prewarning
you could have been prewarning
he could have been prewarning
we could have been prewarning
you could have been prewarning
they could have been prewarning	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't prewarn
you couldn't prewarn
he couldn't prewarn
we couldn't prewarn
you couldn't prewarn
they couldn't prewarn 	I couldn't be prewarning
you couldn't be prewarning
he couldn't be prewarning
we couldn't be prewarning
you couldn't be prewarning
they couldn't be prewarning	I couldn't have prewarned
you couldn't have prewarned
he couldn't have prewarned
we couldn't have prewarned
you couldn't have prewarned
they couldn't have prewarned	I couldn't have been prewarning
you couldn't have been prewarning
he couldn't have been prewarning
we couldn't have been prewarning
you couldn't have been prewarning
they couldn't have been prewarning	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I prewarn?
could you prewarn?
could he prewarn?
could we prewarn?
could you prewarn?
could they prewarn? 	could I be prewarning?
could you be prewarning?
could he be prewarning?
could we be prewarning?
could you be prewarning?
could they be prewarning? 	could I have prewarned?
could you have prewarned?
could he have prewarned?
could we have prewarned?
could you have prewarned?
could they have prewarned? 	could I have been prewarning?
could you have been prewarning?
could he have been prewarning?
could we have been prewarning?
could you have been prewarning?
could they have been prewarning? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I prewarn?
couldn't you prewarn?
couldn't he prewarn?
couldn't we prewarn?
couldn't you prewarn?
couldn't they prewarn? 	couldn't I be prewarning?
couldn't you be prewarning?
couldn't he be prewarning?
couldn't we be prewarning?
couldn't you be prewarning?
couldn't they be prewarning? 	couldn't I have prewarned?
couldn't you have prewarned?
couldn't he have prewarned?
couldn't we have prewarned?
couldn't you have prewarned?
couldn't they have prewarned? 	couldn't I have been prewarning?
couldn't you have been prewarning?
couldn't he have been prewarning?
couldn't we have been prewarning?
couldn't you have been prewarning?
couldn't they have been prewarning?