Shemini Atzeret, meaning "the eighth day of assembly," is a Biblical Jewish holiday that follows the Jewish festival of Sukkot. It is written: "On the eighth day you should hold a solemn gathering; you shall not work at your occupation" (Numbers 29:35).
Praying for Rain
Shemini Atzeret marks the beginning of the rainy season following the harvest in Israel.
The prayer for rain, Tefilat Geshem, is the only ritual that is unique to Shemini Atzeret. In ancient times, an offering was brought to the Temple in Jerusalem on Shemini Atzeret. But once the Temple was destroyed, the only Shemini Atzeret ritual that remained was the liturgy requesting rain for a plentiful year.
After the prayer for rain is recited on Shemini Atzeret, the phrase Masheev HaRuach U-Moreed HaGeshem (He causes the wind to blow and the rain to fall) is inserted into the Amidah prayer until Passover.
Ashkenazi Jews recite the Memorial Prayer, Yizkor, on Shemini Atzeret.
Shemini Atzeret and Sukkot
Even though Shemini Atzeret immediately follows the festival of Sukkot, it is a totally separate holiday. A new Shehechiyanu blessing is recited. And if one sits in the Sukkah on Shemini Atzeret, the prayer recited for sitting in the Sukkah is not recited.
Shemini Atzeret and Simchat Torah
Since the completion of the annual cycle of Torah readings occurred around the time of Shemini Atzeret, a rabbinical tradition developed in the Middle Ages to celebrate the Torah on Shemini Atzeret. This celebration came to be known as Simchat Torah. Simchat Torah celebrates - with joyful processions, singing and dancing - the ending of one cycle of Torah reading and the beginning of a new cycle.
Today in the Diaspora, Simchat Torah is celebrated on the second day of Shemini Atzeret. It is common for Jews in the Diaspora to refer to the first day as Shemini Atzeret and to the second day as Simchat Torah.
In Israel, Simchat Torah is celebrated on the first and only day of Shemini Atzeret. The holiday is referred to as both Shemini Atzeret and Simchat Torah.