pietas

Pietas, pietatis, f., third declension, the abstract noun of pius. Do not reach for "piety" by reflex. Classically it is the whole bundle of duty owed upwards and sideways - to the gods, to the homeland, to parents and children - which is why Aeneas earns the title pius while carrying his father out of burning Troy rather than while sacrificing. Mark the direction of the duty with erga or in plus the accusative, or with a plain objective genitive: pietas in parentes.

Church Latin narrows it to devotion towards God, and that narrowed sense dominates this corpus, so a medieval pietas really is close to "piety". Its opposite is impietas, undutifulness. English pity and pitiful come from the same word by way of French, having slid all the way from duty to compassion.