terabyte

Terabyte is a unit of digital information storage. In the decimal SI system, one terabyte equals 10^12 bytes and is commonly abbreviated TB. In some contexts, however, writers and vendors have informally used terabyte to mean 2^40 bytes, which is technically a tebibyte (TiB).

Bytes and bits: since one byte consists of eight bits, a decimal terabyte holds 8×10^12 bits, and a tebibyte holds 8×2^40 bits.

Usage: terabytes are used to describe storage capacity in hard drives, solid-state drives, and data centers. Storage manufacturers typically label capacities in decimal terabytes, while operating systems may display capacities in binary units such as tebibytes (TiB) or gibibytes (GiB), leading to apparent discrepancies with the decimal TB advertised by manufacturers.

Standards and context: the tera- prefix denotes 10^12 in the SI system. In 1999, the IEC introduced binary prefixes—kibi-, mebi-, gibi-, and tebi-—to resolve ambiguity between decimal and binary multiples. In practice, many products and software still use TB to denote either 10^12 bytes or, informally, 2^40 bytes, depending on the vendor and context.

See also: byte, tebibyte, gibibyte, storage device, file system.