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 couldn't yawn you couldn't yawn she couldn't yawn we couldn't yawn you couldn't yawn they couldn't yawn	I couldn't be yawning you couldn't be yawning she couldn't be yawning we couldn't be yawning you couldn't be yawning they couldn't be yawning
Perfect	V-ing perfect
I couldn't have yawned you couldn't have yawned she couldn't have yawned we couldn't have yawned you couldn't have yawned they couldn't have yawned	I couldn't have been yawning you couldn't have been yawning she couldn't have been yawning we couldn't have been yawning you couldn't have been yawning they couldn't 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
couldn't I yawn? couldn't you yawn? couldn't she yawn? couldn't we yawn? couldn't you yawn? couldn't they yawn?	couldn't I be yawning? couldn't you be yawning? couldn't she be yawning? couldn't we be yawning? couldn't you be yawning? couldn't they be yawning?
Perfect	V-ing perfect
couldn't I have yawned? couldn't you have yawned? couldn't she have yawned? couldn't we have yawned? couldn't you have yawned? couldn't they have yawned?	couldn't I have been yawning? couldn't you have been yawning? couldn't she have been yawning? couldn't we have been yawning? couldn't you have been yawning? couldn't they have been yawning?