inseparable

adjective

• 1unable to be separated or treated separately:research and higher education seem inseparable
• (of people) unwilling to be separated; very close:they met 18 months ago and have been inseparable ever since

• 2 Grammar (of a prefix) not used as a separate word or (in German) not separated from the base verb when inflected.
• (of a German verb) consisting of a prefix and a base verb which are not separated when inflected, for example wiederholen.

noun

• a person or thing inseparable from another.