could concave
Regular verb: concave - concaved- concaved

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could concave
you could concave
she could concave
we could concave
you could concave
they could concave 	I could be concaving
you could be concaving
she could be concaving
we could be concaving
you could be concaving
they could be concaving	I could have concaved
you could have concaved
she could have concaved
we could have concaved
you could have concaved
they could have concaved	I could have been concaving
you could have been concaving
she could have been concaving
we could have been concaving
you could have been concaving
they could have been concaving	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not concave
you could not concave
she could not concave
we could not concave
you could not concave
they could not concave 	I could not be concaving
you could not be concaving
she could not be concaving
we could not be concaving
you could not be concaving
they could not be concaving	I could not have concaved
you could not have concaved
she could not have concaved
we could not have concaved
you could not have concaved
they could not have concaved	I could not have been concaving
you could not have been concaving
she could not have been concaving
we could not have been concaving
you could not have been concaving
they could not have been concaving	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I concave?
could you concave?
could she concave?
could we concave?
could you concave?
could they concave? 	could I be concaving?
could you be concaving?
could she be concaving?
could we be concaving?
could you be concaving?
could they be concaving? 	could I have concaved?
could you have concaved?
could she have concaved?
could we have concaved?
could you have concaved?
could they have concaved? 	could I have been concaving?
could you have been concaving?
could she have been concaving?
could we have been concaving?
could you have been concaving?
could they have been concaving? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not concave?
could you not concave?
could she not concave?
could we not concave?
could you not concave?
could they not concave? 	could I not be concaving?
could you not be concaving?
could she not be concaving?
could we not be concaving?
could you not be concaving?
could they not be concaving? 	could I not have concaved?
could you not have concaved?
could she not have concaved?
could we not have concaved?
could you not have concaved?
could they not have concaved? 	could I not have been concaving?
could you not have been concaving?
could she not have been concaving?
could we not have been concaving?
could you not have been concaving?
could they not have been concaving?