English verb conjugation
CAN YACK

Regular verb: yack - yacked - yacked

Affirmation

Simple form	V-ing form
I can yack you can yack he can yack we can yack you can yack they can yack	I can be yacking you can be yacking he can be yacking we can be yacking you can be yacking they can be yacking
Perfect	V-ing perfect
I can have yacked you can have yacked he can have yacked we can have yacked you can have yacked they can have yacked	I can have been yacking you can have been yacking he can have been yacking we can have been yacking you can have been yacking they can have been yacking

Negation

Simple form	V-ing form
I cannot yack you cannot yack he cannot yack we cannot yack you cannot yack they cannot yack	I cannot be yacking you cannot be yacking he cannot be yacking we cannot be yacking you cannot be yacking they cannot be yacking
Perfect	V-ing perfect
I cannot have yacked you cannot have yacked he cannot have yacked we cannot have yacked you cannot have yacked they cannot have yacked	I cannot have been yacking you cannot have been yacking he cannot have been yacking we cannot have been yacking you cannot have been yacking they cannot have been yacking

Interrogative form

Simple form	V-ing form
can I yack? can you yack? can he yack? can we yack? can you yack? can they yack?	can I be yacking? can you be yacking? can he be yacking? can we be yacking? can you be yacking? can they be yacking?
Perfect	V-ing perfect
can I have yacked? can you have yacked? can he have yacked? can we have yacked? can you have yacked? can they have yacked?	can I have been yacking? can you have been yacking? can he have been yacking? can we have been yacking? can you have been yacking? can they have been yacking?

Interro-negative form

Simple form	V-ing form
can I not yack? can you not yack? can he not yack? can we not yack? can you not yack? can they not yack?	can I not be yacking? can you not be yacking? can he not be yacking? can we not be yacking? can you not be yacking? can they not be yacking?
Perfect	V-ing perfect
can I not have yacked? can you not have yacked? can he not have yacked? can we not have yacked? can you not have yacked? can they not have yacked?	can I not have been yacking? can you not have been yacking? can he not have been yacking? can we not have been yacking? can you not have been yacking? can they not have been yacking?