DVD-14 is an oddball format that doesn't really exist anymore, but was used for a short period of time back in late 1990s and in early years of new millennium when manufacturing of DVD-18 discs was complicated and expensive.
DVD-14 is a two-sided DVD disc that has one side which contains single layer of data and one side which contains two layers of data. In easier terms, the other side of the disc is DVD-5 and the other side of the disc is DVD-9.
DVD-14 disc can hold upto 12.33 gigabytes of data.
Other regular DVD size acronyms are: