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