The Jewish world has a problem with the way Renee Kaplan defines herself: half-Jewish. Kaplan, a television producer in her mid-30s, is the daughter of a Jewish father and a non-Jewish mother who was raised Jewish. "I've had endlessly to defend my half-Jewishness - resist rabbis who wanted to convert me, resent Jewish men who didn't want to date me," she writes in "Half/Life: Jew-ish Tales from Interfaith Homes" (Soft Skull Press, 2006). Kaplan says she rejects anyone who deems her dual identity inauthentic. She is among the increasing number of adult children of intermarriage who consider themselves half-Jewish. While the Jewish religious denominations have varying views of what makes someone Jewish - the Conservative and Orthodox streams count as Jews only those with Jewish mothers, whereas the Reform Related Resources: Overlooked by outreach and Reconstructionist movements sanction Jewish lineage from either side - the denominations are united in their opposition to the notion of one being half-Jewish. You either are or you aren't Jewish, they hold. Yet the "half" term is gaining currency, particularly among those with Jewish fathers and non-Jewish mothers. The phenomenon is encouraged by Web sites, books and groups that celebrate or support these self-proclaimed half-Jews, from www.halfjew.com launched to establish "an identity for HalfJews," to the short-lived student group at Brown University called "The Half-Jew Crew." Many children of intermarriage say they simply cannot turn their backs on the non-Jewish half of their identity. Their rabbis may say they are Jewish, but in their hearts they are also whatever grandma and grandpa are. This openness to multiple identities is particularly true among college students, according to Daniel Klein and Freke Vuijst, who interviewed hundreds of students for "The Half-Jewish Book" published in 2000. Klein says those who call themselves half-Jewish "feel they are a combination, they are an amalgam, they are bicultural." A 2005 survey by Hillel: The Foundation for Jewish Campus Life found that 48 percent of college students who consider themselves Jewish come from intermarried homes. It's from this population that a new subculture is emerging of "people who draw from both sides of their heritage and synthesize their cultural halves into a remarkable new identity," the authors write. It's something to celebrate, not hide, they argue. Klein says his 27-year-old daughter considers herself half-Jewish, though he and Vuijst raised her as a Jew. She dedicated her bat mitzvah speech to her Dutch grandparents, who were honored as "Righteous Gentiles" for saving Jews during the Holocaust. But her divided identity also causes her pain. In Israel on a visit, "everyone said she wasn't Jewish," Klein relates. At college she was kicked out of the kosher food line. Some who use the term are conflicted. Georgiana Cohen, a 27-year-old Web content specialist in Somerville, Mass., was raised by a non-Jewish mother but spent five years at the Donna Klein Jewish Academy in Boca Raton, Fla. That experience, she says, "legitimized a last name I carried around like a fake ID." The split between life at home and at school was stark, she recalls. "My childhood was all Christmas trees and Easter candy," Cohen says. "Meanwhile, back in Boca, I sang folk songs like 'Jerusalem of Gold,' led weekly minyan services with my best friend and captured Hebrew spelling bee trophies." She refers to herself now, somewhat flippantly, as "half-Jewish and half 'fill-in-the-blank.' " Some self-proclaimed half-Jews feel anger as they struggle for a sense of belonging in Jewish denominations that reject their dual identity. In 2006, outreach activist Robin Margolis launched the Half-Jewish Network (www.half-jewish.net), an online community where those with some family connection to Judaism can express themselves openly whether they identify as Jewish, half-Jewish, Christian or nothing. "A lot of these people have been greeted by organizations where the first demand is 'make a choice,' and if they don't, they're not welcome," says Margolis, who attends a Jewish Renewal congregation. The Reform movement, which accepts Jewish patrilineal descent, does not allow children in its religious schools to receive education in a second religion. Some half-Jewish activists believe demography will prove a stronger force than tradition. Nearly half of American Jews are intermarrying, according to the 2000-2001 National Jewish Population Survey. As more of these interfaith families assert their place in the Jewish community, they likely will gain a more influential role in determining how the community views their distinct identity. "We'll be the majority of Jews in this country by 2030," Margolis says. "Then the playing field changes. If we're the majority, we'll decide who's a Jew."