com·ple·tive 
(kəm-plētĭv)
(kəm-plētĭv)n.
A word in a phrase or a morpheme in a word that conveys completeness, such as up in drink up.
- observe
- observer
- observingly
- obsess
- obsession
- obsessional
- obsessionally
- obsessive
- obsessive-compulsive
- obsessive-compulsive disorder
- obsessive-compulsive personality disorder
- obsessively
- obsessiveness
- obsessor
- obsidian
- obsolesce
- obsolescence
- obsolescent
- obsolescently
- obsolete
- obsoletely
- obsoleteness
- obsoletism
- obstacle
- obstacle course