Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could clean clean you could clean clean she could clean clean we could clean clean you could clean clean they could clean clean
V-ing form
I could be clean cleaning you could be clean cleaning she could be clean cleaning we could be clean cleaning you could be clean cleaning they could be clean cleaning
Perfect
I could have clean cleaned you could have clean cleaned she could have clean cleaned we could have clean cleaned you could have clean cleaned they could have clean cleaned
V-ing perfect
I could have been clean cleaning you could have been clean cleaning she could have been clean cleaning we could have been clean cleaning you could have been clean cleaning they could have been clean cleaning
Negation
Simple form
I could not clean clean you could not clean clean she could not clean clean we could not clean clean you could not clean clean they could not clean clean
V-ing form
I could not be clean cleaning you could not be clean cleaning she could not be clean cleaning we could not be clean cleaning you could not be clean cleaning they could not be clean cleaning
Perfect
I could not have clean cleaned you could not have clean cleaned she could not have clean cleaned we could not have clean cleaned you could not have clean cleaned they could not have clean cleaned
V-ing perfect
I could not have been clean cleaning you could not have been clean cleaning she could not have been clean cleaning we could not have been clean cleaning you could not have been clean cleaning they could not have been clean cleaning
Interrogative form
Simple form
could I clean clean? could you clean clean? could she clean clean? could we clean clean? could you clean clean? could they clean clean?
V-ing form
could I be clean cleaning? could you be clean cleaning? could she be clean cleaning? could we be clean cleaning? could you be clean cleaning? could they be clean cleaning?
Perfect
could I have clean cleaned? could you have clean cleaned? could she have clean cleaned? could we have clean cleaned? could you have clean cleaned? could they have clean cleaned?
V-ing perfect
could I have been clean cleaning? could you have been clean cleaning? could she have been clean cleaning? could we have been clean cleaning? could you have been clean cleaning? could they have been clean cleaning?
Interro-negative form
Simple form
could I not clean clean? could you not clean clean? could she not clean clean? could we not clean clean? could you not clean clean? could they not clean clean?
V-ing form
could I not be clean cleaning? could you not be clean cleaning? could she not be clean cleaning? could we not be clean cleaning? could you not be clean cleaning? could they not be clean cleaning?
Perfect
could I not have clean cleaned? could you not have clean cleaned? could she not have clean cleaned? could we not have clean cleaned? could you not have clean cleaned? could they not have clean cleaned?
V-ing perfect
could I not have been clean cleaning? could you not have been clean cleaning? could she not have been clean cleaning? could we not have been clean cleaning? could you not have been clean cleaning? could they not have been clean cleaning?