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