A Bat Mitzvah is the female counterpart to the Bar Mitzvah.
Bat = Daughter (Ashkenazic pronunciation is 'Bas'), Mitzvah = Commandment. This is the ceremony that marks the transition of a Jewish girl into a responsible adult, usually taking place on her 12th birthday. This primarily means that she is now responsible morally and religiously, and is formally expected to observe the commandments of the Torah and Judaism*. No party or ceremony is strictly required; the Bat Mitzvah takes place automatically. Even so, it is common for a Bat Mitzvah to be celebrated in one way or another.
For the most part, the information in the Bar Mitzvah node also applies to the Bat Mitzvah; in many cases there is no difference between the Bar Mitzvah and the Bat Mitzvah. Things that may be different for the girls include:
- A Bat Mitzvah often takes place at 12, not 13. (Sometimes a range of 12-14 is given as the proper age; in theory the onset of puberty is the primary qualification, although this is often ignored in practice). While 12 is the more traditional age, and probably the more usual, many synagogues prefer holding both Bat and Bar Mitzvahs at age 13.
- In Orthodox, Chasidic Judaism, and some sects of Conservative Judaism females are not permitted to serve in religious services such as getting an aliyah or to count in a minyan. The Bat Mitzvah is usually still celebrated with some sort of party.
The celebration of the Bat Mitzvah is also a much more recent occurrence than is celebrating a Bar Mitzvah. The Bar Mitzvah ceremony as we celebrate it today (more or less) dates back to the 1200s or 1300s; the Bat Mitzvah ceremony was formally started in 1922. While in some areas of Europe the Bat Mitzvah was celebrated as long as 200 years ago, this did not include any reading of the Torah or other religious responsibilities.
The Bat Mitzvah, as a ceremony on par with the Bar Mitzvah, was started by Mordecai Kaplan, the founder of Reconstructionist Judaism. He wanted to have some sort of ritual marking his daughter's Bat Mitzvah; he found no good reason why females shouldn't have much the same ceremonial duties as men -- although others disagreed. Niddah, the impurity of females due to menstruation, had traditionally kept women from reading or reciting the Torah. Kaplan argued that since there was no Temple, it was therefore not necessary to keep the temple pure. And since there was no red heifer with which to preform the ceremony of the red heifer, no one was truly pure. Thus there was no reason to uphold the ban against women; there wasn't truly any purity that need protection from them**. Even so, the Bat Mitzvah didn't really start to catch on until the 1950s.
The first recorded modern Bat Mitzvah took place on the morning of March 18, 1922, when twelve-year old Judith Kaplan recited a few blessings and read portions of the Torah at the bimah of her father's synagogue. Mordecai Kaplan observed "No thunder sounded. No lightning struck."
The early Bat Mitzvah was most often limited to Friday nights (not an 'official', ritual, Torah reading, in other words), and limited to the haftarah, or, if the girl was allowed to read from the Torah, she was kept from using the Sefer Torah. Nowadays males and females are usually treated equally.
AKA Bath Mitzvah, Bat Mizvah, Bas Mitzvah and Bas Mizvah. It may or may not be capitalized.
* Children are encouraged to follow the commandments for the most part, but are not required to. Fasting, for example, is rarely observed by young children.
** I have been able to find very little information on Mordecai Kaplan's actual arguments; I hope I'm not misrepresenting his position, or putting words into his mouth. If you have any comments on this, let me know.