ROME — Pope Francis is very much a pastor, so when he speaks he typically uses homespun imagery that’s easy to grasp. It doesn’t require any special insight, for instance, to get the point when he counsels married couples that it’s okay to “let the dinner plates fly” when they fight, as long as they don’t go to bed mad.

On the other hand, there are times when Francis falls back on specialized argot not always clear to the rest of the world.

For one thing, when he veers off the cuff in Spanish he’ll sometimes drop in a term or two in porteño, the dialect of his native city of Buenos Aires in Argentina, which even native Spanish-speakers from other places may not recognize. In Brazil in 2013, for instance, he urged young people to cause lio in the Church, and it took a while to realize he meant something like “make some noise.”

An Argentine journalist named Jorge Milia, who studied under the future pope, has written a series of articles for the Vatican newspaper translating porteño terms of which Francis is fond. They’re called “Bergoglioisms” in reference to the pope’s given name, Jorge Mario Bergoglio.

No matter what language Francis is speaking, however, there’s also a cluster of key words that have become part of his standard talk on the stump. They all have precise meanings to him, but they can be unclear or open to misinterpretation for those who haven’t followed him closely.

Here, then, is a brief guide to “decoding” Pope Francis ahead of his Sept. 22 arrival in the United States, focusing on six terms that may pop up in one or more of the 18 speeches he’ll give, and which will be either unfamiliar or easily taken the wrong way.

Periphery

Francis repeatedly has called the Catholic Church to “go to the peripheries,” and he doesn’t just mean the geographic margins of the world.

Certainly physical peripheries are part of it – explaining, for instance, Francis’ drive to lift up cardinals from places such as Haiti, Myanmar, and Tonga, and the instructions he’s given to include venues on his foreign journeys that have never seen a pope before. (In Cuba, that’s why he’s going to city of Holguín in addition to Havana and Santiago.)

For the pope, however, “periphery” is also a metaphor for everyone who’s in some way marginalized or vulnerable, including immigrants and refugees, the poor, the elderly, the unborn, and so on, as well as topics he considers too long neglected, such as the Christian duty to care for creation.

Although Francis knows there are plenty of peripheries in the United States, both physical and existential, for him this trip takes him to one of the perceived centers of the world. As a result, it’s likely that at some point along the line, he’ll feel compelled to call on the center not to forget the periphery.

(Indeed, in a sense he’s broadcasting that message to Americans even before he arrives by beginning the trip in Cuba.)

Mercy

Mercy is a cornerstone spiritual concept for Francis, reflected in his official motto, miserando atque eligendo, which means roughly “choosing through the eyes of mercy.” In a similar vein, the slogan for his trip to Cuba is “missionary of mercy.”

It’s so important to Francis that he’s called a special Jubilee Year of Mercy to run from Dec. 8, 2015, to Nov. 20, 2016, and he’s made special concessions for the year, such as giving all priests permission to grant forgiveness for abortion.

Francis uses “mercy” in its classic Christian sense, meaning that it’s not an alternative to judgment. He’s not abolished the concept of sin, as one Italian journalist fancifully imagined in late 2013. From the traditional perspective, mercy enters the picture only after one believes that sin has been committed.

The pontiff’s emphasis on mercy is key to understanding just what kind of a revolutionary, or a reformer, he really is. He’s not changing doctrine, but rather how doctrine is applied. He wants to shift the church towards the most compassionate and forgiving possible way of living its traditional teaching.

Francis is the “pope of mercy,” but that doesn’t mean he’s succumbed to what philosophers call “relativism,” meaning rejecting an objective difference between right and wrong. Listen to Francis talk about greed, for instance, and it’s clear this pope is no relativist.

Fundamentalism

In American Protestantism, the term “fundamentalist” is often used without any pejorative connotation to mean a Biblical conservative. It comes from a set of essays written by influential Protestant authors in the 1910s and published by the Bible Institute of Los Angeles called “The Fundamentals,” defending Christian orthodoxy.

When Francis criticizes fundamentalists – which he did again just three days ago, saying fundamentalists “take God away from His people” – he doesn’t have the American Protestant sense of the word in mind. Instead, for him “fundamentalist” is equivalent to “extremist,” almost a religious terrorist.

If Francis blasts “fundamentalism” in the States, therefore, he won’t mean it as a gratuitous poke in the eye at people who believe in the inerrancy of the Bible, but rather as way of denouncing violence and hatred carried out in the name of God.

Ideological colonization

As history’s first pope from the developing world, Francis is keenly sensitive to perceived imbalances of power between the West and everyone else. One area he believes it shows up is efforts by Western governments and NGOs, as well as the U.N. and other global bodies, to force poor countries to abandon their traditional values as the price of receiving development assistance.

What Francis means by “ideological colonization,” for instance, would be an U.N. agency offering an African nation funding for anti-AIDS campaigns on the condition that they reduce population by a specific percentage, or allow distribution of condoms in their public clinics, or revise public school textbooks to promote family planning, or legalize same-sex marriage.

That’s what Francis had in mind when he said in the Philippines in January, for instance, that “there’s an ideological colonization we have to be careful of that tries to destroy the family.”

The phrase may come up in the States, perhaps when Francis addresses the General Assembly of the United Nations in New York on Sept. 25.

Gender theory

For most Americans, “gender theory” probably sounds like the name of a graduate seminar in a Women’s Studies program. Francis, however, uses it to mean efforts to eradicate the biological differences between men and women, or to treat those differences as culturally conditioned and therefore optional.

That’s what he had in mind during a General Audience in April, for instance, when he said, “I wonder if so-called gender theory may not also be an expression of frustration and resignation that aims to erase sexual differentiation because it no longer knows how to come to terms with it.”

“Getting rid of the difference is the problem, not the solution,” he said.

In an interview in February with two Italian journalists, Francis called gender theory a “sin” that fails to “recognize the order of creation.”

Given that background, if Francis talks about “gender theory” while he’s in the States, it probably will be a clue he’s about to say something that will appeal to the cultural right.

“Devil’s Dung”

At least three times, Pope Francis has referred to money as the “devil’s dung,” attributing the line to the 4th century saint, bishop, and theologian Basil of Caesarea. (In fact, Basil never used that precise phrase, though he did write a letter to a rich young man who decided to become a monk to praise him for “treating all your perilous property as mere dung.”)

“Devil’s dung” is obviously a colorful soundbite, and whenever people refer to Francis’ anti-capitalist rhetoric, this is a large part of what they have in mind.

In context, however, it’s never capital in itself Francis has in mind when he complains about “devil’s dung,” but something akin to the sin of idolatry. Here, for instance, is what he said in Bolivia in July speaking to representatives of social movements:

“Once capital becomes an idol and guides people’s decisions, once greed for money presides over the entire socioeconomic system, it ruins society, it condemns and enslaves men and women, it destroys human fraternity, it sets people against one another and, as we clearly see, it even puts at risk our common home.”

For sure, Francis is a critic of many aspects of the way global capitalism operates in the early 21st century. His beef, however, isn’t really with the system, but rather the distorted values that sometimes skew it against the poor.

In other words, when Francis talks about “devil’s dung,” he isn’t trying to deliver an economics lesson. It’s a moral exhortation, a way of insisting that any social structure should serve people — especially, in his mind, those at the peripheries — rather than the other way around.