The pontiff explained that piety, or "pietà" – which in Italian can also be translated as compassion, pity, or mercy – should not "be confused with compassion which we feel for the animals who live with us."
"It happens, in fact, that at times one feels this sentiment toward animals, and remains indifferent to the suffering of one's brothers and sisters," he added.
The May 14 gathering at the Vatican was the latest in a series of special audiences for the Jubilee Year of Mercy, which are being held throughout the year in addition to the weekly general audiences on Wednesdays.
The Jubilee of Mercy is an Extraordinary Holy Year that officially commenced December 8 – the Solemnity of the Immaculate Conception – with the opening of the Holy Door in St. Peter's Basilica. It will close Nov. 20, 2016 with the Solemnity of Christ the King.
Pope Francis centered Saturday's catechesis on piety with regard to those "who need love." Piety is an aspect of mercy, and one of the Seven Gifts of the Holy Spirit, he said.
As noted in the English language synthesis of the address, the word piety denotes a sense of "religiosity or devotion," but it also relates to compassion and mercy.
The concept of piety existed in the Greco-Roman world, the Pope explained in Italian, where it referred to being submissive toward superiors, such as the gods, one's parents, the elderly, etc.