uncertain= not sure

 

uncommon= rare; not the usual; remarkable

 

unconscious= not within thought; not awake

 

undecided= not yet at the point of making a decision

 

unexpected= not what someone thought would happen; not predicted

 

unmistakable= clear; cannot be understood the wrong way; not able to be confused or misunderstood

 

unnecessary= not required

 

untidy= messy; not neat; not organized

 

unwise= not smart

 

unworthy= not deserving; not having any value