stand-alone

Operating, functioning, or existing without additions or assistance; independent; able to be separate or separated; not attached to anything.

They offer an inexpensive add-on for a computer, or a stand-alone system with all the functions built in.

Make sure your music software is stand-alone, too (ie, it doesn’t have to be loaded into a utility—we don’t want to have to mess around with bits of wire or umpteen different programs just to hear your maestropiece).

Not part of a series, or not requiring familiarity with that series.

a stand-alone sequel

A device that can operate on its own, rather than as an accessory for another device.

Standalone systems, also known as dedicated systems, are often thought to provide word processing cervices alone. In truth, some standalones — but not all of them — can be used for other functions as well. […] Also, some standalones can only be used for word processing; if you need other computer functions, you can't have them.

Something that is not a part of some series or sequence.

Near-synonym: one-off

This standalone will delight and draw readers of Christian romantic suspense like […]