The Gemara in Shabbos 94b (Mishna 10:6) refers for the first time to an issur derabanan as a shevus. Is there a rule when an issur derabanan is referred to as a shevus and when not?
Gershon
I did not see anyone address your question specifically, but this is the way it appears to me:
There are two kinds of Isurei Shevus on Shabbos. As the Rambam (Hilchos Shabbos 22:1) writes, "There are Shevusim that the Rabanan prohibited because they are similar to Melachos, and there are Shevusim that the Rabanan prohibited because they might lead to the transgression of an Isur Sekilah."
The Gemara refers to the former as "Shevus" all the time, since they are not Gezeiros but rather enactments in deference of the commandment "Shabason -- Shevos!" (see Magid Mishnah there, and Gemara Shabbos 114b). An example of these is Amirah l'Nochri, which the Gemara always refers to as Shevus, or moving objects from or into a Karmelis.
When addressing the second category (Gezeiros of Shabbos), the Gemara seems to call them Shevus only when in order to contrast them to an Isur d'Oraisa, e.g. when we first mentioned an Isur d'Oraisa, and then listed these as "only Shevusim."
I hope this is helpful,
M. KORNFELD
The Gemara records in a number places that Rebbi does not prohibit a "Shevus" from being performed Bein ha'Shemashos (see Shabbos 8b Rashi DH v'Rebbi Hi d'Amar, even though he is referring to any Isur d'Rabanan of Shabbos. Does this fit with what you wrote?
With regard to Amirah l'Akum, the expression "Shevus" became a borrowed term used for any Isur performed through Amirah l'Akum, see Bava Metzia 90a, and especially Tosfos Rosh Hashanah 24b DH Sha'ani, see also Shach on Shulchan Aruch YD 141:23, etc.
Kol Tuv,
Yitzchok Zirkind
The Takanah prohibiting the transfer of objects to a Karmelis is in the first category of Shevus; the Isur was enacted because moving to a Karmelis is similar to a Melachah. That is why the word "Shevus" is always appropriate when describing a Melachah involving a Karmelis.
Although Rebbi is including any Isur d'Rabanan of Shabbos in his Heter, it is specifically applied in the Mishnah to tranferring an object to or from a Karmelis, which is why he mentions the word "Shevus" in that statement.
M. Kornfeld