1. (machine word, computer word) A vector of bits that is treated as a unit by the computer hardware. The number of bits is referred to as the word length or word size. Word lengths of 32 bits are common in home computers, and word lengths of 64 bits are not uncommon in professional and scientific workstations. The memory of a computer is divided into words (and possibly subdivided into bytes). A word is usually long enough to contain an instruction or an integer. See also memory hierarchy.

2. (string) In formal language theory, a finite sequence of symbols drawn from some set of symbols Σ‎. This is then a word over the alphabet Σ‎ or a Σ‎-word. The elements of Σ‎ are also called letters. Common notation includes:

• |w|—the length of the word w,

• w_i—the ith symbol in w,

• Λ‎, the empty word—the unique word of length 0,

• Σ‎*—the set of all Σ‎-words.

Σ‎* is infinite unless Σ‎ is empty, in which case