Often heard with the word “Shabbat,” an oneg is a celebration, a gathering. It is more than a quick cup of coffee together, and less than a “function.” It often implies food, though sometimes the focus is on music, dance, entertainment, even a lecture. Oneg (עֹנֶג) means “pleasure” or “delight.”
The usage with “Shabbat” seems to have originated from the notion of taking sheer physical enjoyment in Shabbat. “If you call the Shabbat a delight, the Lord’s holy day is honored….” (Isaiah 58:13.) And the rabbis have discussed how to do this! Rabbi Yehudah said that the requirement of oneg could be fulfilled through eating spinach, large fish, and heads of garlic. Rav Pappa said it could be even something small like little fish fried in oil and flour (Talmud Shabbat 118b). Over the years, discussion has leaned toward all such pleasures - three meals of the best food and drink we can afford, marital bliss, appreciating the world.
Some synagogues may distinguish between “oneg” and “kiddush” by marking the former as Friday night and the latter as Saturday morning. “Kiddush” means “sanctification” or “separation.” (We are advised to separate the Shabbat from the rest of the week.) It also implies an attendant glass of wine over which we recite a blessing before enjoying. Often even when Jews could not afford good wine they would get treacly raisin wine. Thus thick, sweet kosher wine is often called “kiddush wine.”
Of course there are other “kiddushes,” too: kiddush levanah, the sanctification of the moon, kiddush hahodesh, blessing the new month, and so on. Oneg, though, is always “pleasure” and “delight.”
We might take this opportunity to look at yet another word, the entire opposite of oneg: ones (אֹנֶס). Ones refers to compelling someone to act against the person’s will, or the happening of events that cause a negative event or prevent a positive one. It can be used to refer to rape, threat of death, physical torture, or financial loss. Such behavior certainly puts a major onus on the victim, not to mention the court systems.
Let’s stick with oneg. Note on page 189 in Siddur Lev Shalem, you will see the concept mentioned within the Musaf Amidah, “Yismehu vemalekhutekha shomerei Shabbat vekorei oneg…” (Let’s sing!) Shabbat Shalom!