One class is a subtype of another class if all the operations of the second class of object also apply to objects of the first type - perhaps in a different way. Subtypes shown by the generalization arrow that has an open arrow head. T U V
In the hierarchy of user-defined datatypes, a subtype is always a dependent on its supertype.
A classification of virus among influenza types A viruses. Currently, there are 15 subtypes of type A influenza.