English verb conjugation
COULD CONCENTER

Regular verb: concenter - concentered - concentered

Affirmation

Simple form	V-ing form
I could concenter you could concenter he could concenter we could concenter you could concenter they could concenter	I could be concentering you could be concentering he could be concentering we could be concentering you could be concentering they could be concentering
Perfect	V-ing perfect
I could have concentered you could have concentered he could have concentered we could have concentered you could have concentered they could have concentered	I could have been concentering you could have been concentering he could have been concentering we could have been concentering you could have been concentering they could have been concentering

Negation

Simple form	V-ing form
I couldn't concenter you couldn't concenter he couldn't concenter we couldn't concenter you couldn't concenter they couldn't concenter	I couldn't be concentering you couldn't be concentering he couldn't be concentering we couldn't be concentering you couldn't be concentering they couldn't be concentering
Perfect	V-ing perfect
I couldn't have concentered you couldn't have concentered he couldn't have concentered we couldn't have concentered you couldn't have concentered they couldn't have concentered	I couldn't have been concentering you couldn't have been concentering he couldn't have been concentering we couldn't have been concentering you couldn't have been concentering they couldn't have been concentering

Interrogative form

Simple form	V-ing form
could I concenter? could you concenter? could he concenter? could we concenter? could you concenter? could they concenter?	could I be concentering? could you be concentering? could he be concentering? could we be concentering? could you be concentering? could they be concentering?
Perfect	V-ing perfect
could I have concentered? could you have concentered? could he have concentered? could we have concentered? could you have concentered? could they have concentered?	could I have been concentering? could you have been concentering? could he have been concentering? could we have been concentering? could you have been concentering? could they have been concentering?

Interro-negative form

Simple form	V-ing form
couldn't I concenter? couldn't you concenter? couldn't he concenter? couldn't we concenter? couldn't you concenter? couldn't they concenter?	couldn't I be concentering? couldn't you be concentering? couldn't he be concentering? couldn't we be concentering? couldn't you be concentering? couldn't they be concentering?
Perfect	V-ing perfect
couldn't I have concentered? couldn't you have concentered? couldn't he have concentered? couldn't we have concentered? couldn't you have concentered? couldn't they have concentered?	couldn't I have been concentering? couldn't you have been concentering? couldn't he have been concentering? couldn't we have been concentering? couldn't you have been concentering? couldn't they have been concentering?