must concenter
Regular verb: concenter - concentered- concentered

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

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not concenter
you must not concenter
he must not concenter
we must not concenter
you must not concenter
they must not concenter 	I must not be concentering
you must not be concentering
he must not be concentering
we must not be concentering
you must not be concentering
they must not be concentering	I must not have concentered
you must not have concentered
he must not have concentered
we must not have concentered
you must not have concentered
they must not have concentered	I must not have been concentering
you must not have been concentering
he must not have been concentering
we must not have been concentering
you must not have been concentering
they must not have been concentering	

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

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not concenter?
must you not concenter?
must he not concenter?
must we not concenter?
must you not concenter?
must they not concenter? 	must I not be concentering?
must you not be concentering?
must he not be concentering?
must we not be concentering?
must you not be concentering?
must they not be concentering? 	must I not have concentered?
must you not have concentered?
must he not have concentered?
must we not have concentered?
must you not have concentered?
must they not have concentered? 	must I not have been concentering?
must you not have been concentering?
must he not have been concentering?
must we not have been concentering?
must you not have been concentering?
must they not have been concentering?