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Rabbi Edward Zerin jokes that “anyone under 90 is a kid.”

Easy to say when you’re 94, but it’s indicative of the San Francisco retired rabbi’s easy sense of humor and youthful take on life.

The spry nonagenerian takes daily walks from his Cathedral Hill apartment, reads extensively and admits he is always scribbling notes and working on his next project.

His 10th and latest book, “A Tribute to My Teacher Rabbi Simon Krinsky,” was released in December 2013. Published by the Jewish Historical Society of Delaware, it is a collection of 60 poems translated by Zerin from Yiddish to English.

“All my publications go back to previous things in my life,” Zerin says in describing how the book came about. Krinsky was born in Poland, ordained in pre-state Israel, immigrated to the U.S. and settled in Delaware, which is where his and Zerin’s paths crossed.

Krinsky played a pivotal role in Zerin’s Jewish life — first as his bar mitzvah teacher and later as a mentor when Zerin was preparing to enter Hebrew Union College, the Reform rabbinical seminary in Jerusalem.

Krinsky died in 1977.

A few years ago while in Boston for his grandson’s wedding, Zerin took a day trip to the National Yiddish Book Center in Amherst. Over the years Zerin has translated for the center, and his grandson interned and studied there.

“I found Rabbi Krinky’s book, ‘The Present and the Past,’ “ Zerin says. “I looked at the poems, all in Yiddish, and decided to pay tribute to my teacher and translate them into English.”

Though Yiddish comes easily to Zerin, translating is tedious work, especially when it comes to poetry, he admits. It took about a year to complete the project.

Zerin addressed the challenges inherent in poetry translation in two ways. “First, I was honest,” he says, “then, I counted the meters in the line and tried to replicate them. Second, I did not try to do the rhyming,”

Zerin grew up in a Yiddish-speaking household in Delaware. “Very often I still think in Yiddish,” he says. “Whenever I ruminate, it’s almost second nature and Yiddish phrases just flow out.”

He even corresponds in Yiddish with his grandson.

Zerin’s love of the language is evident as he explains that, just as a word in English (or any other language, for that matter) can express an idea, so, too, does Yiddish. “When you say ‘Shabbat,’it’s not just ‘the seventh day of the week, Saturday,’ ” he explains. “It’s the table, the idea, the history, the magic, the wonder, the pleasure and the study.”

Yiddish is not his only love. Zerin has worn many professional hats in his nine decades, working as a college professor, licensed marriage and family therapist, congregational rabbi, and consultant on Judaism for Catholic textbooks. He has authored tens of dozens of articles on everything from Jewish education to love and sex.

He was ordained as a rabbi in 1946, received a doctorate in 1952 from the University of Southern California, and has continued his quest for knowledge throughout his life. A fellowship at Boston University in the 1970s enabled him to meet philosopher Karl Popper, with whom he became lifelong friends.

Zerin moved to the Bay Area 10 years ago from Westlake Village, CA, where he was worked as a psychotherapist.

What brought him here? Love.

“I married my present wife twice,” he says with a smile, explaining that after presiding over Jill Kneeter’s nuptials in 1956, the two later struck up a friendship through the mail after their respective partners had died. “We kind of hit it off,” he says.

After meeting each other’s adult children, Zerin says it “felt comfortable” and the two were married. The ceremony took place in October 2004 in their living room; Congregation Emanu-El’s former rabbi, Stephen Pearce, and Rabbi Helen Cohn officiated.

Zerin, while “very satisfied” with his current book, is already looking forward to tackling his next project.

“I am very interested in the relationship between science and Judaism,” he says. We live in most interesting times today, and I believe that it is important to look at what Judaism can offer to science and what science can contribute to Judaism.”

But at 94, he says, “How many books can you write at one time?”

“A Tribute to My Teacher” by Rabbi Edward Zerin (194 pages, Jewish Historical Society of Delaware, $9.95)