English verb conjugation
COULD YAWN

Regular verb: yawn - yawned - yawned

Affirmation

Simple form	V-ing form
I could yawn you could yawn she could yawn we could yawn you could yawn they could yawn	I could be yawning you could be yawning she could be yawning we could be yawning you could be yawning they could be yawning
Perfect	V-ing perfect
I could have yawned you could have yawned she could have yawned we could have yawned you could have yawned they could have yawned	I could have been yawning you could have been yawning she could have been yawning we could have been yawning you could have been yawning they could have been yawning

Negation

Simple form	V-ing form
I could not yawn you could not yawn she could not yawn we could not yawn you could not yawn they could not yawn	I could not be yawning you could not be yawning she could not be yawning we could not be yawning you could not be yawning they could not be yawning
Perfect	V-ing perfect
I could not have yawned you could not have yawned she could not have yawned we could not have yawned you could not have yawned they could not have yawned	I could not have been yawning you could not have been yawning she could not have been yawning we could not have been yawning you could not have been yawning they could not have been yawning

Interrogative form

Simple form	V-ing form
could I yawn? could you yawn? could she yawn? could we yawn? could you yawn? could they yawn?	could I be yawning? could you be yawning? could she be yawning? could we be yawning? could you be yawning? could they be yawning?
Perfect	V-ing perfect
could I have yawned? could you have yawned? could she have yawned? could we have yawned? could you have yawned? could they have yawned?	could I have been yawning? could you have been yawning? could she have been yawning? could we have been yawning? could you have been yawning? could they have been yawning?

Interro-negative form

Simple form	V-ing form
could I not yawn? could you not yawn? could she not yawn? could we not yawn? could you not yawn? could they not yawn?	could I not be yawning? could you not be yawning? could she not be yawning? could we not be yawning? could you not be yawning? could they not be yawning?
Perfect	V-ing perfect
could I not have yawned? could you not have yawned? could she not have yawned? could we not have yawned? could you not have yawned? could they not have yawned?	could I not have been yawning? could you not have been yawning? could she not have been yawning? could we not have been yawning? could you not have been yawning? could they not have been yawning?