Definition: MLC

(MultiLevel Cell) A NAND flash memory technology that stores more than one bit per cell. The original "single level cell" (SLC) flash memory uses one voltage threshold to define the two states of the bit (0 or 1). A multilevel cell (MLC) stores two bits per cell, while triple level (TLC) stores three, and quad level (QLC) stores four. All of this is accomplished by detecting different voltage levels (see below). However, the more bits per cell, the less longevity of the drive (see SSD write cycle). See NAND flash, StrataFlash and TRIM support.

Consumer MLC (cMLC) and Enterprise MLC (eMLC)
MLC generally refers to consumer MLC (cMLC), while enterprise MLC (eMLC) chips provide greater durability for servers that handle huge volumes of reads and writes. Enterprise MLC features faster transfer rates along with extensive error detection and correction.

Even More Cells - From 2D to 3D
Multilevel cell technology doubled, tripled and quadrupled the bits per cell; however, moving from 2D single layer flash to 3D layers dramatically increased storage capacity (see NAND flash).

  Cell    No. of   No. of
  Type     Bits    Values

  SLC       1        2

  MLC/eMLC  2        4

  TLC       3        8

  QLC       4       16

Triple Level Cells in 3D