What does enumerable mean?
'Enumerable' is a formal adjective meaning capable of being counted, listed, or named one by one. When a collection of things is enumerable, each element can in principle be assigned a number and set down in order — whether it is the handful of objections raised at a meeting or the items in a warehouse inventory. The word also has an important technical life in mathematics and computer science: there, an 'enumerable' set may be genuinely infinite yet still countable, provided its members can be matched one-to-one with the natural numbers, as with the even numbers. Related phrases such as 'recursively enumerable' describe sets for which an algorithm can generate every valid member. Because 'enumerable' sits so close in sound to 'innumerable' — its near-opposite — writers should take care not to confuse the two. Precise, slightly technical, and quietly useful, the word signals careful, systematic thinking about quantity.
adjectiveCapable of being counted or listed one by one; able to be enumerated. In mathematics, specifically describes an infinite set whose elements can be put into one-to-one correspondence with the natural numbers.
- Able to be counted or listed item by item.
- (Mathematics and logic) Describing an infinite set whose elements can be placed in one-to-one correspondence with the natural numbers; also, describing a language or formal system for which there exists an algorithm that lists all and only its valid elements.
"The auditor verified that every expense in the report was enumerable and could be matched to a receipt."
"The committee's concerns were few enough to be enumerable on a single page."
"The set of all even numbers is infinite, yet it is enumerable because each element corresponds to a natural number."
In computer science, a set can be infinite and still enumerable — as long as you can imagine numbering its elements one by one, infinity itself becomes listable.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of enumerable
'Enumerable' derives from the Latin verb 'enumerare', meaning 'to count out' or 'to reckon up', formed from 'e-' (out) plus 'numerare' ('to number'), itself from 'numerous', meaning 'number'. The term entered English via Late Latin 'enumerabilis'. It shares this root with 'enumerate', 'enumeration', 'number', and 'numerous', all ultimately tracing back to the same Indo-European root underlying words for counting and reckoning across many European languages.
Related word forms
How enumerable is actually used
Predominantly formal or technical register. Outside of mathematics, logic, and computer science, 'countable' is usually preferred in everyday English. In mathematics the term carries a precise technical meaning distinct from its everyday sense — an 'enumerably infinite' set is a specific kind of infinity.
Easily confused with enumerable
'Innumerable' means too many to be counted, whereas 'enumerable' means capable of being counted or listed.
'Numerous' simply means many, while 'enumerable' specifically indicates that items can be individually counted or listed.