What does it mean to be Jewish in America? A new Pew Research Center survey finds that many Jewish Americans participate, at least occasionally, both in some traditional religious practices – like going to a synagogue or fasting on Yom Kippur – and in some Jewish cultural activities, like making potato latkes, watching Israeli movies or reading Jewish news online. Among young Jewish adults, however, two sharply divergent expressions of Jewishness appear to be gaining ground – one involving religion deeply enmeshed in every aspect of life, and the other involving little or no religion at all.

Overall, about a quarter of U.S. Jewish adults (27%) do not identify with the Jewish religion: They consider themselves to be Jewish ethnically, culturally or by family background and have a Jewish parent or were raised Jewish, but they answer a question about their current religion by describing themselves as atheist, agnostic or “nothing in particular” rather than as Jewish. Among Jewish adults under 30, four-in-ten describe themselves this way.

At the same time, younger Jewish adults are much more likely than older Jews to identify as Orthodox. Among Jews ages 18 to 29, 17% self-identify as Orthodox, compared with just 3% of Jews 65 and older. And fully one-in-ten U.S. Jewish adults under the age of 30 are Haredim, or ultra-Orthodox (11%), compared with 1% of Jews 65 and older.

Meanwhile, the two branches of Judaism that long predominated in the U.S. have less of a hold on young Jews than on their elders. Roughly four-in-ten Jewish adults under 30 identify with either Reform (29%) or Conservative Judaism (8%), compared with seven-in-ten Jews ages 65 and older.