The Chachamim established the recital of Kaddish at the conclusion of each stage of the prayer service. After the recital of the Korbanot, Kaddish d’Rabbanan is recited; after the conclusion of Pesukei d’Zimrah, Half-Kaddish; after Nefillat Apayim and Tachanunim, Half-Kaddish; following Kedushah d’Sidra, Kaddish-Titkabal is recited; after Shir Shel Yom, Mourner’s Kaddish (Kaddish Yatom); and after Pitum HaKetoret, Kaddish d’Rabbanan (Shibolei HaLeket 8). With the Kaddish, we close each stage of the prayer service and elevate it towards the most supreme objective, the respect of Heaven, and from there we continue on to the next stage.
There are four versions of Kaddish: 1) Half-Kaddish. This is the essence of the Kaddish. It is called Half-Kaddish so as to distinguish it from other Kaddishim which contain further additions. In any section of prayer where a prolonged interruption is undesirable, Half-Kaddish is recited. 2) Kaddish Yehei Shelama, also called Kaddish Shalem (Full-Kaddish). This is recited after saying verses of Scripture, and contains an added request for peace and good life for us and for all Israel. We conclude, “Oseh shalom bimromav… v’imru Amen”. Since this Kaddish is usually recited by people who have lost a parent, it is also called Kaddish Yatom (Mourner’s Kaddish). 3) Kaddish-Titkabal. The chazan recites this Kaddish after the conclusion of the Amidah. In it, before the addition of Kaddish Shalem, a request is added that our prayers be accepted. 4) Kaddish d’Rabbanan. This Kaddish is recited after learning rabbinic teachings. Before the addition of Kaddish Shalem, we add a prayer in this Kaddish for those who learn Torah, that they should merit long and prosperous lives.
Responding Amen to these additions is not as important as responding to the main part of the Kaddish. Therefore, one may not interrupt the recital of Birkot Keriat Shema and Pesukei d’Zimrah in order to respond to them.
. According to the opinion of the Mishnah Berurah 66:17, one who is in the middle of Birkot Keriat Shema or Pesukei d’Zimrah responds to the Kaddish in two places: “Amen, yehei Shemei rabba mevorach l’alam ul’almei almaya,” and also “Amen” at the end. According to the Kaf HaChaim 66:23, he responds with all five Amens in the main part of the Kaddish. See the laws of Birkot Keriat Shema in this book, 16:5.
It is important to state that according to Minhag Sephard, the chazan says “v’yitzmach purkanei vikarev meshichei” in the wording of the Kaddish and the congregation responds Amen, whereas in Minhag Ashkenaz, those four words are not recited. The root of this difference lies in the teachings of the Geonim. In Siddur Rav Amram Gaon and Machzor Vitri, the Kaddish is written like Minhag Ashkenaz, and in Siddur Rav Sa’adyah Gaon and in the Rambam it is like Minhag Sephard, although only “v’yitzmach purkanei” is mentioned (see Netiv Binah, part 1, p. 366). Further, it should be noted that in the main part of the Kaddish this is the only distinction; however, at the end of the Kaddish, there are many differences, for in the main part of the prayer the original nusach that Chazal instituted was better preserved. But, in the additions made by the sages of the generations after the scattering of the exiles, the discrepancies between the wordings are more pronounced.