Editing Is-a (section)

== Related concepts ==
The ''is-a'' relationship is to be contrasted with the ''[[has-a]]'' (''has_a'' or ''has a'') relationship between types (classes); confusing the relations ''has-a'' and ''is-a'' is a common error when designing a model (e.g., a [[computer program]]) of the real-world relationship between an object and its subordinate. The ''is-a'' relationship may also be contrasted with the ''[[Typeof|instance-of]]'' relationship between objects (instances) and types (classes): see [[Type–token distinction]].

To summarize the relations, there are:

* [[hyperonym]]–[[hyponym]] (supertype/superclass–subtype/subclass) relations between types (classes) defining a taxonomic hierarchy, where
** for a [[Inheritance (object-oriented programming)|subsumption]] relation: a hyponym (subtype, subclass) has a ''type-of'' (''is-a'') relationship with its hyperonym (supertype, superclass);
* [[holonym]]–[[meronym]] (whole/entity/container–part/constituent/member) relations between types (classes) defining a possessive hierarchy, where
** for an [[Aggregation (object-oriented programming)|aggregation]] (i.e. without ownership) relation:
*** a holonym (whole) has a ''has-a'' relationship with its meronym (part),
** for a [[Composition (object-oriented programming)|composition]] (i.e. with ownership) relation:
*** a meronym (constituent) has a ''[[part-of]]'' relationship with its holonym (entity),
** for a [[Object composition#Containment|containment]]<ref>See also [[Containment (computer programming)]].</ref> relation:
*** a meronym (member) has a ''member-of'' relationship with its holonym ([[Container (abstract data type)|container]]);
* concept–object (type–token) relations between types (classes) and objects (instances), where
** a token (object) has an ''[[Instance (computer science)|instance-of]]'' relationship with its type (class).