In formal language theory, the alphabet is defined as which of the following?

In formal language theory, the alphabet is defined as which of the following?

• A. A set of words
• B. A set of symbols or tokens
• C. A set of rules
• D. A set of sentences

Answer: (B)

In formal language theory, the alphabet is the basic building blocks—the set of symbols or tokens from which strings are formed. These are the characters you can use to create any string in the language, like {0, 1} or {a, b, c, …}. A string is simply a finite sequence of these symbols. The language, which is what you’re often ultimately describing, is the set of strings that meet certain criteria; it is built from the alphabet but is not the alphabet itself. The other options describe larger constructs: a set of words would be a language or a subset of it, and a set of rules defines the grammar that governs how strings are assembled. A set of sentences is also a language or a collection within a language, not the basic symbol set.

In formal language theory, the alphabet is the basic building blocks—the set of symbols or tokens from which strings are formed. These are the characters you can use to create any string in the language, like {0, 1} or {a, b, c, …}. A string is simply a finite sequence of these symbols. The language, which is what you’re often ultimately describing, is the set of strings that meet certain criteria; it is built from the alphabet but is not the alphabet itself. The other options describe larger constructs: a set of words would be a language or a subset of it, and a set of rules defines the grammar that governs how strings are assembled. A set of sentences is also a language or a collection within a language, not the basic symbol set.