Pierre Joris, a poet and translator who tackled some of the 20th century’s most difficult verse, rendering into English the complex work of the German-Romanian poet Paul Celan, died on Feb. 27 at his home in Brooklyn. He was 78.

His wife, Nicole Peyraffite, said the cause was complications of cancer.

Mr. Joris was the author of dozens of volumes of his own poetry and prose. But much of his life’s work was spent grappling with the poetry of Celan, whom many critics considered, in the words of one scholar, “arguably the greatest European poet in the postwar period.”

That greatness comes with a hitch for readers, though: the fiendish difficulty of a writer whose lyrics were formed and deformed by the crucible of the Holocaust — “that which happened,” as Celan termed it. Both his parents were murdered by the Nazis in what is now Romania. Less than 30 years later, Celan put an end to his own life in France, jumping into the Seine river in 1970 at the age of 49.

In between, he felt he had to invent a new version of German, the cultured language he was brought up in as a member of the Jewish bourgeoisie in Czernowitz (now part of Ukraine). But it had to be cleansed of Nazi barbarism.

The result would be “truly an invented German,” as Mr. Joris (pronounced JOR-iss) wrote in the introduction to “Breathturn Into Timestead” (2014), his translations of Celan’s later works.

A public reading of Celan’s best-known work, the hypnotic “Death Fugue,” was “an epiphany” for Mr. Joris as a 15-year-old high school student in his native Luxembourg, he told the New York State Writers Institute in 2014. The poem was inspired by the murder of Celan’s mother in 1942.

“My hair stood on end,” Mr. Joris recalled.

The poem, as translated by Mr. Joris, begins:

Black milk of morning, we drink you at dusktime
we drink you at noontime and dawntime we drink you at night
we drink and we drink

But “Death Fugue” was an early work, later partly disavowed by Celan. It is the enigmatic poetry of his final years that Mr. Joris was determined to take on.

The “untranslatability” of late Celan “is a truism in critical discussion,” the poet and critic Adam Kirsch wrote in The New York Review of Books in 2016, in a largely favorable review of Mr. Joris’s work.

Mr. Joris took on the challenge. “He did the impossible, because it is impossible to translate Celan,” the Romanian-American poet Andrei Codrescu said in an interview.

In eight books of translations published over more than 50 years, beginning when he was an undergraduate at Bard College in 1967, Mr. Joris sought to render in English Celan’s experiment with language: to transmit what can’t be rendered in words — the Holocaust and its many aftermaths, physical and psychological — by creating an open-ended poetry of multiple possible meanings.

Celan’s poetry “is the work that came out of the mid-20th century that most directly addresses the disaster, if you want, of Western culture,” Mr. Joris told the Los Angeles Review of Books in 2021.

“The absolute poem — no, it certainly does not, cannot, exist,” Celan said in a famous speech in Germany in 1960, when he was awarded a literary prize. And so the translator of Celan has latitude, which Mr. Joris took advantage of — to mostly good effect, in the eyes of critics.

Celan’s “view is bound to destabilize any concept of the poem as some fixed and absolute artifact,” Mr. Joris commented in his introduction to “Breathturn.”

At the level of the words themselves, a translator might thus opt for what Mr. Joris termed “elegant, easily readable and accessible American versions of German.” He rejected that approach.

Instead, he tried to recreate Celan’s many startling neologisms in English, as the Princeton critic Michael Wood noted, citing, among many other examples, “starred-over,” “ensummered,” “night-cradled,” “day-removed,” “worlddownward” and “more heartnear.”

“There are some words that I’m still looking for, that I haven’t found yet,” Mr. Joris told the writer Paul Auster in a public dialogue at Deutsches Haus in New York in 2020. “Fearful polysemy.”

While some critics found this approach heavy-handed, Mr. Wood praised Mr. Joris’s adventurousness. “A poet himself, he is not afraid of strangeness in diction,” Mr. Wood wrote in the London Review of Books in 2021. “He doesn’t seek it out, but he knows when it sounds good. He brings us very close to Celan at work, shows him leading the words along and being led by them, as Celan himself describes the process.”

In an interview with the poet Charles Bernstein in 2023, Mr. Joris referred to Celan as “the bruised, weary, suspicious survivor who prefers to communicate through his poems, poems meant to ‘witness for the witness.’”

Mr. Joris, raised in Luxembourg, the tiny duchy caught between the French- and German-speaking worlds, identified with the linguistic confusion of Celan’s own upbringing in German and Romanian. Mr. Joris grew up speaking the local Germanic dialect, Luxembourgish, as well as German and French. (He called French the “language of the bourgeoisie.”)

Luxembourg, he told Mr. Auster, “has the same complexities of language that Celan grew up in.”

“That polyglot nature of Celan’s upbringing, we share that,” he added.

Pierre Joseph Joris was born on July 14, 1946, in Strasbourg, France, to Roger Joris, a surgeon, and Nora Joris-Schintgen, who assisted her husband’s practice as an administrator. He graduated from the Lycée Classique in Diekirch, Luxembourg, in 1964, briefly studied medicine in Paris to fulfill the wishes of his parents, and then moved to the United States, where he earned a B.A. from Bard in 1969.

In 1975, he received a master’s degree from the University of Essex in England in the theory and practice of literary translation. From 1976 to 1979, he taught in the English department of Université Constantine 1 in Algeria. He earned a Ph.D. in comparative literature from the State University of New York at Binghamton in 1990 and taught at SUNY Albany from 1992 to 2013.

In addition to his translations of Celan, Mr. Joris published several volumes of his own poetry, including “Poasis: Selected Poems 1986-1999” (2001) and “Barzakh: Poems 2000-2012” (2014); books of essays, including “A Nomad Poetics” (2003); and translations of Rilke, Edmond Jabès and other poets. He also edited anthologies, including the two-volume “Poems for the Millennium: The University of California Book of Modern and Postmodern Poetry,” with Jerome Rothenberg (1995 and 1998).

In addition to his wife, a performance artist, he is survived by a son, Miles Joris-Peyrafitte; a stepson, Joseph Mastantuono; and a sister, Michou Joris.

Asked to explain why he was drawn to translating, Mr. Joris told the periodical Arabic Literature in 2011: “Because, by accident of birth, I was blessed or damned with a batch of different languages and a perverse pleasure of pitting them and their different musics against each other.”