The empty set, also known as the null set, is a set with no elements. It is denoted by the symbol ∅.

In linguistics, an alphabet is a set of symbols used to represent the sounds of a spoken language.

The intersection of two sets A and B, denoted by A ∩ B, is the set of elements that are common to both A and B.

In linguistics, concatenation is a set operation that combines two strings of symbols into a single string.

The union of two sets A and B, denoted by A ∪ B, is the set of elements that are in either A or B or both.

In linguistics, vocabulary refers to the set of words used in a language.

The complement of a set A with respect to a universal set U, denoted by Aᶜ, is the set of elements in U that are not in A.

In linguistics, merging is a set operation that combines two or more sets of symbols into a single set.

The power set of a set A, denoted by P(A), is the set of all subsets of A.

In linguistics, phonemes are the smallest units of sound that can distinguish one word from another.

The Cartesian product of two sets A and B, denoted by A × B, is the set of all ordered pairs (a, b) where a ∈ A and b ∈ B.

In linguistics, composition is a set operation that combines two or more linguistic structures into a single structure.

The relation between two sets A and B, denoted by A → B, means that every element of A is also an element of B.

In linguistics, nouns are a set of words that refer to people, places, things, or ideas.

The inverse relation of a relation R from A to B, denoted by R⁻¹, is the relation from B to A that consists of all ordered pairs (b, a) such that (a, b) ∈ R.