olemus
ISO 13584:
klass, mille kõik liikmed on ühtlasi mingi ta alamklassi liikmed
= class of which all members are also members of one of its subclasses

ülevaateid
https://en.wikipedia.org/wiki/Class_(computer_programming)#Abstract_and_concrete

https://www.softwareideas.net/uml-abstract-class