stand-alone

Short definition from Wiktionary

Adjective

1. 1
   Operating, functioning, or existing without additions or assistance; independent; able to be separate or separated; not attached to anything.
2. 2
   Not part of a series, or not requiring familiarity with that series.

Noun

1. 1
   A device that can operate on its own, rather than as an accessory for another device.
2. 2
   Something that is not a part of some series or sequence.