An enumerative definition of a concept or term is a special type of

extensional definition In logic, extensional and intensional definitions are two key ways in which the objects, concepts, or referents a term refers to can be defined. They give meaning or denotation to a term. Intensional definition An intensional definition gives m ...

that gives an explicit and exhaustive listing of all the

object Object may refer to: General meanings * Object (philosophy), a thing, being, or concept ** Object (abstract), an object which does not exist at any particular time or place ** Physical object, an identifiable collection of matter * Goal, an ...

s that fall under the concept or term in question. Enumerative definitions are only possible for finite sets and only practical for relatively small sets. An example of an enumerative definition for the set ;

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

monotreme Monotremes () are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals (Eutheria), and marsupials (Metatheria). Monotremes are typified by structural differences in their brain ...

species (for which the intensional definition is ''species of currently-living mammals that lay eggs'') would be :

platypuses The platypus (''Ornithorhynchus anatinus''), sometimes referred to as the duck-billed platypus, is a semiaquatic, egg-laying mammal endemic to eastern Australia, including Tasmania. The platypus is the sole living representative or monotyp ...

: echidnae: ::

short-beaked echidna The short-beaked echidna (''Tachyglossus aculeatus''), also called the short-nosed echidna, is one of four living species of echidna and the only member of the genus ''Tachyglossus''. It is covered in fur and spines and has a distinctive snou ...

:: long-beaked echidnae: :::

Sir David's long-beaked echidna Sir David's long-beaked echidna (''Zaglossus attenboroughi''), also known as Attenborough's long-beaked echidna or the Cyclops long-beaked echidna, is one of the three species from the genus '' Zaglossus'' that occurs in New Guinea. It is named i ...

:::

eastern long-beaked echidna The eastern long-beaked echidna (''Zaglossus bartoni''), also known as Barton's long-beaked echidna, is one of three species from the genus '' Zaglossus'' to occur in New Guinea. It is found mainly in the eastern half at elevations between . Des ...

:::

western long-beaked echidna The western long-beaked echidna (''Zaglossus bruijnii'') is one of the four extant echidnas and one of three species of '' Zaglossus'' that occurs in New Guinea. Originally described as ''Tachyglossus bruijnii'', this is the type species of ''Zag ...

See also