DVD being the most common.
DVD was originally used as an initialism for the unofficial term digital videodisc.
A newsgroup FAQ written by Jim Taylor (a prominent figure in the industry) claims that four years later, in 1999, the DVD Forum stated that the format name was simply the three letters "DVD" and did not stand for anything.
The DVD Forum website has a section called "DVD Primer" in which the answer to the question, "What does DVD mean?" reads, "The keyword is 'versatile.' Digital Versatile Discs provide superb video, audio and data storage and access—all on one disc."
Read more about DVD: Identification (MID), Capacity, DVD Recordable and Rewritable, Dual-layer Recording, DVD-Video, DVD-Audio, Blu-ray Disc/HD DVD, Use As Backup Medium