enumerate

Enumerate is a verb meaning to name elements of a set one by one or to count them off in order. In writing, an enumerated list presents items in a sequential, numbered form. The noun enumeration refers to the act of listing or the resulting sequence. The word comes from Latin enumerare, meaning to recount or add up.

In mathematics and computer science, enumerable (or countable) describes sets that can be listed in a sequence. A finite set is enumerable, and an infinite set is enumerable if its elements can be put into a one-to-one correspondence with the natural numbers. Common examples are the natural numbers; the set of rational numbers is also enumerable, while many real numbers are not, depending on the chosen notion of enumeration.

In programming, enumerate commonly refers to a function that pairs each element of a sequence with its index. In Python, enumerate(iterable, start=0) yields pairs (index, value) as you iterate. Separately, enum or enumeration type refers to a data type that defines a fixed set of named constants, used to improve readability and maintain type safety in languages such as C, Java, and Rust. The term also appears in the broader sense of producing a list of items programmatically.