Chazal say that when 3 people eat together they are obligated in a zimun: I am having trouble defining what it means to be kovua seuda together. In Yeshivas people eat at the same time and place but I often see no zimun being made. Is kevuas more then just sitting down and talking to one’s neighbor? If one doesn’t talk to the people at the table does that make a difference? If people eat together but never planned on it does that matter? I know the gemara talks about a case where 2 people are done eating and a 3rd joins and the gemara basically says that if the original people would still eat in theory, they are machayiv in a zimun even if they don’t eat anymore. I know this is a general question, but after going through the Shulchan Aruch on this topic I am lacking a clear definition. Thank you!
The principle that is outlined by Shluchan Aruch (193:2-4), as understood by many authorities (Chemed Moshe 5, Maamar Mordechai 7, Chayei Adam 48:2, as cited by Machatzis Hashekel 10, Kaf Hachaim 22, Shaar Hatzion 16; see also Taz), is that if a group begins eating together, or ends the meal together, they are obligated in making a zimun. If they neither started together, nor ended together, one should not make a zimun. This ruling is based on Tosafos in Berachos (45a).
However, a number of authorities understand that most rishonim disagree with the distinction made by Tosafos, and rule that zimun is obligatory even when a third person joins the first two in the middle of the meal. [The same would apply to four people who join six who began together, with regard to a zimun with the name of Hashem.] This opinion is found in Eliyah Rabba (8), Nahar Shalom (3), and Aruch Hashulchan (16), the latter writing that one should not be lenient in this matter. According to this opinion, the very act of eating together obligates zimun, though this is only stated when two out of the three started eating together.
See also Peri Megadim (M.Z. 6), who mentions grounds for leniency based on the principle the the obligation of zimun is rabbinic.
What is considered ‘eating together’? Rema (20 writes, based on Beis Yosef quoting from Riva, that even when no zimun is obligatory, it is better to make a zimun. Many poskim maintain that this applies to separate tables: Bach, Perishah, Kenesses Hagedolah, and so on. Magen Avraham (8), however, rules that for separate tables one may not make a zimun, and the zimun is only made when those eating are seated, at least partially, at the same table. Others dispute the proofs and opinion of Magen Avraham (see Eliyah Rabba; Aruch Hashulchan), but Mishnah Berurah (24) cites his ruling, and quotes (from Peri Megadim) that for zimun with the name of Hashem, one should certainly be stringent.
With regard to yeshivos, it is interesting to note that Or Letzion (II, p. 114) writes that yeshiva students don’t really “eat together” during the week, each one coming and leaving at his own convenience, and therefore a zimun with the name of Hashem should not be made unless somebody declares at the beginning: “let’s eat!”
However, Shulchan Aruch (167:11) implies that eating at the same table is always considered a kevius together, and for yeshiva students who know other, study together, and see themselves as “one big family,” it would seem that even separate tables would be considered eating together, provided they started eating at the same time. This is also the ruling given by Minchas Yitzchak (XIII, no. 8, sec. 3) and by Yalkut Yosef (III, p. 375), and this is the common custom in yeshivos.
Therefore, provided that at least two people began to eat together, a zimun should be made in yeshivos, even by those seated at different tables, and the more so when all are seated at the same table. This would apparently apply even for making a zimun with the name of Hashem, provided that six people began eating together.