can alter
Verbo regular: alter - altered- altered

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I can alter
you can alter
he can alter
we can alter
you can alter
they can alter 	I can be altering
you can be altering
he can be altering
we can be altering
you can be altering
they can be altering	I can have altered
you can have altered
he can have altered
we can have altered
you can have altered
they can have altered	I can have been altering
you can have been altering
he can have been altering
we can have been altering
you can have been altering
they can have been altering	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I cannot alter
you cannot alter
he cannot alter
we cannot alter
you cannot alter
they cannot alter 	I cannot be altering
you cannot be altering
he cannot be altering
we cannot be altering
you cannot be altering
they cannot be altering	I cannot have altered
you cannot have altered
he cannot have altered
we cannot have altered
you cannot have altered
they cannot have altered	I cannot have been altering
you cannot have been altering
he cannot have been altering
we cannot have been altering
you cannot have been altering
they cannot have been altering	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can I alter?
can you alter?
can he alter?
can we alter?
can you alter?
can they alter? 	can I be altering?
can you be altering?
can he be altering?
can we be altering?
can you be altering?
can they be altering? 	can I have altered?
can you have altered?
can he have altered?
can we have altered?
can you have altered?
can they have altered? 	can I have been altering?
can you have been altering?
can he have been altering?
can we have been altering?
can you have been altering?
can they have been altering? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can I not alter?
can you not alter?
can he not alter?
can we not alter?
can you not alter?
can they not alter? 	can I not be altering?
can you not be altering?
can he not be altering?
can we not be altering?
can you not be altering?
can they not be altering? 	can I not have altered?
can you not have altered?
can he not have altered?
can we not have altered?
can you not have altered?
can they not have altered? 	can I not have been altering?
can you not have been altering?
can he not have been altering?
can we not have been altering?
can you not have been altering?
can they not have been altering?