DVD-18

DVD-18 in an acronym that means a two-sided DVD disc with two layers of data on both sides of the disc -- in other terms, it is a two-sided disc that holds DVD-9 disc on both sides of it.

DVD-18 disc can contain upto 15.9 gigabytes of data on it (with 7.95 gigabytes on each side).

Other regular DVD size acronyms are:
-DVD-5
-DVD-9
-DVD-10
-DVD-14