In the past few months, my daughter Ellie has become a “Who Is A Jew” adjudicator of sorts.

At 3 ½ years old, she knows nothing about matrilineal or patrilineal descent, nor has she any clue about what is recognized by the State of Israel — or for that matter, what exactly Israel is.

But newly cognizant of the fact that she is Jewish, and that Jewishness is not universal, she has become fascinated with categorizing everyone she knows, sorting them into “Jewish” and “Christian.”

She is Jewish. Her friends Owen and Stephanie are Christian. The other kids at Tot Shabbat are Jewish. Her babysitter Maria is Christian.

Since virtually all our friends and family are, in fact, Jewish or Christian, however secular, I have not yet complicated the picture by elaborating on Islam, Buddhism and the myriad of other religions represented just within our ZIP code.

And not always being certain myself what constitutes Jewishness, I’ve so far stuck to a very functional template for the Tribe-Gentile dichotomy. Jews celebrate Shabbat, Chanukah and other Jewish holidays, while Christians celebrate Christmas and Easter. Jews go to temple, and Christians go to church. Jews have mezuzot on their doors; Christians don’t.

But even for a small child, 21st-century Judaism’s messy realities and ubiquitous exceptions to the rules make things confusing. She celebrates Easter and Christmas at school, yet she is Jewish. For weeks, she insisted that her friend Milo Goldman could not be Jewish, because his front door — four floors above ours — has no mezuzah.

Most perplexing, however, is how to categorize Ellie’s lapsed Catholic father.

One day as she is reeling off the roster of Jews and Christians we know, Ellie turns to Joe and says, “You’re Jewish, right Dad?”

“Well, no,” he says.

“Oh, you’re Christian?”

“I’m Catholic,” he says, chafing a little at being lumped together with the Protestant heretics.

“But you have a mezuzah,” she says. “You don’t go to church. You go to temple. And you celebrate Shabbat.”

Indeed, Joe has become as committed to our Friday night rituals as I, joining in with all the blessings, especially the “ha’gafen” part of the kiddush, which in an affectionate pun, he likes to pronounce “hug often.”

“I know, but I’m still Catholic,” he explains.

Perhaps it’s just because she’s at the developmental stage of endlessly recycled conversations, but she proceeds to return to this discussion again and again. And I can’t help but wonder if the repeated questioning comes because she has not gotten a satisfying response, and because she senses our own discomfort with the topic — in the same way that we hem and haw when she asks about Joe’s father, who died when he was a child, or when she demands to know the whereabouts of Helen, the Jewish Week receptionist who passed away in December.

After a few more rounds of the “Is Dad Jewish?” conversation, I offer, “Well, he’s sort of Jewish,” which puts the questioning to an end for a while.

I don’t want Ellie to be confused or upset by the fact that her dad is different from her, although I suppose it’s not the only way he is different. After all, he is male and she is female. He’s older and bigger than she is and has considerably less hair on his head. Maybe Ellie will just grow up, like the majority of American Jewish kids today, accepting as normal that some members of the family are Jewish and others are not.

I ask my friend Leah, who was raised Jewish, if she can remember being Ellie’s age and realizing that her father was not Jewish. Was there some traumatic, formative moment? (In my childhood home, Freudianism supplanted Judaism, so I’m always on the alert for formative traumas.)

But Leah doesn’t recall being troubled by it until she got to Hebrew school, where she didn’t fit in with the other girls and wondered if it was because she was half Indian and thus looked different. (Today, she thinks it has more to do with her parents’ smaller bank account.)

For Marc Marrero, a Jewish day school grad who is now a student at Tufts University, the “moment” came when he was about 8 and decided to buy holiday presents for friends and family.

“At that point, things became complicated,” he writes in an e-mail interview from Spain, where he is spending a semester. “My dad got Christmas wrapping paper, my friends ‘Jewish’ wrapping paper, and I just remember wishing that it could be simpler — that everyone could be either Jewish or Catholic. Or at least that I wouldn’t have to worry about which presents needed which wrapping paper.”

Mary Ellen Markowitz, a Catholic whose twin daughters just celebrated their b’nei mitzvah, remembers one Chanukah night when the girls were in fifth grade. One of them said, “Mom, I’m very down,” and started weeping. After exploring other possibilities, Markowitz, who is a social worker with a degree in child development, asked, “Do you think it’s because I’m not Jewish?”

Her daughter replied, “That’s it, Mommy. You’re not me.”

“I said, ‘I’ll never be Jewish, but I love your religion and love what you’re learning,’” Markowitz recalls.

Markowitz urges me to be “very neutral and very natural,” in responding to Ellie’s questions. “Say this is what our family’s all about. Mommy’s this, Daddy’s that and we’ve decided to raise you this. Children accept that. … These are normal questions, almost like, ‘Why do you have dark hair and Daddy has blond hair?’” n

“In The Mix” appears the third week of the month. To read past columns, go to http://intermarried.wordpress.com. E-mail julie.inthemix@gmail.com.