(n.) 1. With reference to CDs, the method of storing code and data. There are two basic modes. In mode 1, used with CD-ROM applications, 288 bytes of each sector are used to store error correction code, and the remaining 2048 bytes per sector store data. Mode 2, used in CD-i and CD-ROM XA, has two forms. Form 1 is similar to mode 1 in that it has Red Book error correction. Form 2 discs allow 2336 bytes per sector of non–error corrected data for information storage; this capacity is used most commonly for graphic and audio content. 2. Oscillation that may be propagated in an electromagnetic field within a waveguide. Laser-generated light exhibits modes in an optical fiber.