For a group of new-to-America students at Northeast High School, the letter "C" doesn't stand for Cat.

It stands for Culture. And "D" is for Dreamer, "M" for Memory, "V" for Visa.

You can bet that "B" doesn't stand for Build the Wall.

The Immigrant Alphabet — printed on 26 big banners now set on the glass walls and windows of the Municipal Services Building in Center City — forms the heart of an eye-catching outdoor art installation that distills the challenges, hopes, and losses encountered in coming to a new country. Even the background colors are symbolic, white to suggest newness, blue for loneliness.

It's a signature project of Welcoming Week, a city celebration meant to forge bonds among neighbors and cast Philadelphia as an open, embracing community for immigrants, refugees, and people of all backgrounds. But what for four years had been a pleasant, low-key cultural festival opened Friday with a new urgency amid the nation's contentious debate over immigration.

"The rhetoric we've been hearing on the national stage has been so negative around immigrants," said Miriam Enriquez, director of the city Office of Immigrant Affairs, which runs the event. "Our slogan, 'Welcoming immigrants and connecting communities,' that's the goal. When people learn about each other, it really cultivates peace and understanding. That might sound cliché, but it's true."

For newcomers and their allies, this month has been punishing.

It began with President Trump announcing his intent to revoke the Deferred Action for Childhood Arrivals program, or DACA, which shields nearly 800,000 undocumented immigrant young people from deportation. Last week, however, he appeared to have reached an agreement with Democratic legislators to extend DACA protections for those who were illegally brought here as children. By week's end, the president insisted that no such deal existed. He told reporters that no action would be taken unless his promised southern border wall was included in the legislation, but also that the wall could come later.

In two weeks, he is expected to set a new, lower limit on the number of refugees who can come to the United States.

The president is keeping his campaign promise — get tough on immigration.

Welcoming Week, running through Sept. 25, takes the opposite approach.

In Philadelphia — one of 100 participating Welcoming Week communities from Maine to California — an aim is to provide U.S.- and foreign-born residents with a chance to explore and understand different cultures. Events will take place across the city. The schedule is so packed that the week actually lasts 11 days, full of international music and food, flag-raisings, seminars, and hard-fought soccer action in the annual Unity Cup tournament.

On Sunday, the Penn Museum hosts Dark Waters — 2,379 Days and Counting, an art project in response to the Syrian refugee crisis. At 11 a.m. in Stoner Courtyard, visitors can help craft 2,379 small tin boats, which at 5 p.m. will be set afloat in a fountain as part of a live and live-streamed work by Syrian-born artist Issam Kourbaj. It's a variation on his well-known Strike, where tiny boats carried cargoes of burnt matches, a metaphor for the light and dark of each day in crisis.

Philadelphia's foreign-born population has surged in the last decade, to about 200,000, or 13 percent of city residents, a Pew Research Center analysis found. Roughly one in four is undocumented, Pew said. Philadelphia officials credit new arrivals with not only boosting the city population, currently 1,567,900 after decades of decline, but also with starting businesses, fixing homes, and making their communities better.

The city has been a leader in the so-called Sanctuary City movement, seeking to treat undocumented residents the same as anyone else when they come in contact with the criminal-justice system.

"Philadelphia will continue to be a diverse and welcoming city," Mayor Kenney pledged to students, mentors, and program leaders at the Welcoming Week kickoff in City Hall.

On Cottman Avenue, a Northeast High that once was a bastion of the white working class now ranks among the city's most diverse schools. Its 3,400 students come from 49 countries and speak 57 languages. Many are refugees from war and violence, fleeing immediate danger and now facing daunting longer-term challenges in language, education, and employment.

The Immigrant Alphabet sprang from collaboration between Hudson Valley artist Wendy Ewald and 18 students, and was developed under the auspices of Al-Bustan Seeds of Culture, a nonprofit that examines Arab culture through art and language. Ewald and Al-Bustan project director Diana Misdary spent months with students who in some cases are still struggling to understand how and why they came here — and still gathering the courage to share their stories.

"I wanted people to understand that not everyone is the same," said Gabrielle Oho, a 16-year-old junior from Saint Lucia, an island in the eastern Caribbean. "Some people go through hard times trying to come over here."

Ewald and the students chose the alphabet as a vehicle because it's both familiar and elemental, key to language and learning. At the same time, the alphabet can be childlike and playful and fun. Some of the student banners could be at home on Sesame Street, if the subject weren't so serious.

Rushami Nasimova chose the letter "L."

"I picked it because I was forced to leave my country," said the 20-year-old Northeast High graduate. "The government would kill my mom, because she was a journalist. For me, [the L] was just a feeling, an expression. 'We are leaving everything in the past and coming to a new country.'"

She, her mother, and three siblings came from Tajikistan, in Central Asia, undertaking a five-year journey to safety that included stops in Turkey and Russia.

"I picked 'U' – Upset," said 17-year-old Amariah Bashir, a senior who came from Pakistan five years ago. "You got to leave your country and all your friends? That's upset."

In the students' alphabet, "B" stands for Border, "O" for Occupy, "S" for stereotype. The letter "T" is for trust, "H" for happiness.

For Aya Mahde, a 15-year-old sophomore from Iraq, a single letter can't contain her experience, including the death of her father and her journey through Syria and Jordan to reach America two years ago.

She wonders what people will make of the alphabet, so prominent in its place across from City Hall.

"Some people will just see pictures," she said. "Other people will have a lot of feelings."