Simachot is the popular, though euphemistic name for tractate Avel Rabbati ("the Great Mourning"). It is widely called Simachot ("joyous occasions") due to the reluctance to refer to a tractate by a name with such negative connotation. Simachot is part of a series known as the Misechtot Kitanot ("small tractates"), tractates that include Tannaic teachings, but were not included by Rabbi Judah the Prince in the orders of the Mishnah. There is no Talmudic commentary on these tractates. (In the standard printed Talmud, these tractates can be found in the back of the volume that contains tractate Avodah Zarah.)

Tractate Simachot discusses the laws that pertain to people on their deathbed, funerals, burials, and mourning.

Starting with midday the day before Tisha b'Av and continuing through the fast day, it is only permitted to study sections of Torah that do not "gladden the heart." As such, siyums made on these two days are either on Simachot or Moed Kattan, which also concludes with the laws of mourning.

The1 Sages instituted the drinking of ten cups of wine at meals held in a mourner's home: Three drunk together with the appetizers, three drunk together with the entrée, and four after the meal, during the Grace after Meals—one for each of the four blessings in the Grace.

At a later time, another four cups were added to the original ten: One in honor of the city's public servants (who preoccupy themselves with burying the dead); one in honor of the city philanthropists (who kindly cover the interment costs of those too poor to pay the expenses); one for the Holy Temple (for whose destruction we mourn, and we pray that G‑d consoles us through its rebuilding); and one in honor of Rabbi Gamliel.

(The Talmud in Ketubot explains why Rabbi Gamliel merited this special cup in his honor: Originally the expense of burying the dead was so prohibitive – due to the expensive, exquisite shrouds commonly used – that relatives started abandoning the bodies of their deceased next of kin! Rabbi Gamliel, before passing away, instructed that he be enshrouded in simple linen [though he was a very wealthy man]. Everyone followed suit, and people were spared the outrageous expense formerly associated with burial.)

Because of the quantity of wine being imbibed – fourteen cups – people started getting drunk at these repasts (especially inappropriate given the setting), so the Sages restored the institution to its original arrangement: only ten cups.

One2 who recites the Grace after Meals in the house of a mourner, what does he say for the fourth blessing?3 The Sages are of the opinion that the standard Hatov v'haMetiv is recited; Rabbi Akiva says that the Hatov v'haMetiv is substituted for the following blessing: "[Blessed are You...] the true Judge, ruler over His creations, righteous judge of all generations, of Whom we are all subjects and servants, and, no matter what, we are obliged to thank and bless Him."

One who sees a site wherein miracles were performed for the Jews, says, "Blessed [is the One] who performed miracles for our ancestors in this place. Praise G‑d for He is good, for His kindness is everlasting."4