Definition: A grandfather clause (or grandfather policy) is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from the new rule are said to have grandfather rights or acquired rights, or to have been grandfathered in.
Notes: Cyfyd yn aml yng nghyd-destun hawliau gan ffermwyr i chwsitrellu plaleiddiaid. Argymhellir defnyddio'r ddau air tafodieithol mewn deunyddiau i Gymru gyfan, ond gellid ei addasu yn ôl cyd-destun y gynulleidfa darged.
