Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could breath you could breath he could breath we could breath you could breath they could breath
V-ing form
I could be breathing you could be breathing he could be breathing we could be breathing you could be breathing they could be breathing
Perfect
I could have breathed you could have breathed he could have breathed we could have breathed you could have breathed they could have breathed
V-ing perfect
I could have been breathing you could have been breathing he could have been breathing we could have been breathing you could have been breathing they could have been breathing
Negation
Simple form
I couldn't breath you couldn't breath he couldn't breath we couldn't breath you couldn't breath they couldn't breath
V-ing form
I couldn't be breathing you couldn't be breathing he couldn't be breathing we couldn't be breathing you couldn't be breathing they couldn't be breathing
Perfect
I couldn't have breathed you couldn't have breathed he couldn't have breathed we couldn't have breathed you couldn't have breathed they couldn't have breathed
V-ing perfect
I couldn't have been breathing you couldn't have been breathing he couldn't have been breathing we couldn't have been breathing you couldn't have been breathing they couldn't have been breathing
Interrogative form
Simple form
could I breath? could you breath? could he breath? could we breath? could you breath? could they breath?
V-ing form
could I be breathing? could you be breathing? could he be breathing? could we be breathing? could you be breathing? could they be breathing?
Perfect
could I have breathed? could you have breathed? could he have breathed? could we have breathed? could you have breathed? could they have breathed?
V-ing perfect
could I have been breathing? could you have been breathing? could he have been breathing? could we have been breathing? could you have been breathing? could they have been breathing?
Interro-negative form
Simple form
couldn't I breath? couldn't you breath? couldn't he breath? couldn't we breath? couldn't you breath? couldn't they breath?
V-ing form
couldn't I be breathing? couldn't you be breathing? couldn't he be breathing? couldn't we be breathing? couldn't you be breathing? couldn't they be breathing?
Perfect
couldn't I have breathed? couldn't you have breathed? couldn't he have breathed? couldn't we have breathed? couldn't you have breathed? couldn't they have breathed?
V-ing perfect
couldn't I have been breathing? couldn't you have been breathing? couldn't he have been breathing? couldn't we have been breathing? couldn't you have been breathing? couldn't they have been breathing?