Article 2 of the EU MDR discusses the terms and definitions. There are around 71 terms and definitions whereas some chosen terms are discussed below: 
Accessory for a Medical Device
It is defined as "an article which, whilst not being itself a medical device, is intended by its manufacturer to be used together with one or several particular medical devices to specifically enable the medical devices to be used in accordance with their intended purposes or to specifically and directly assist the medical functionality of the medical devices in terms of their intended purposes."