An Accessory

1. Something that belongs to part of another main thing; something additional and subordinate, an attachment.
2. (fashion) An article that completes one's basic outfit, such as a scarf or gloves.
3. (law) A person who is not present at a crime, but contributes to it as an assistant or instigator.
4. (art) Something in a work of art without being indispensably necessary, for example solely ornamental parts.

Synonyms

• (something that belongs to part of another main thing): accompaniment, addition, attachment, supplement; adjunct
• (one who assists in or instigates an offense): abettor, accomplice, ally, coadjutor, accessary