Conversion to Judaism (Hebrew: גיור, giyur) is a religious act when, after a period of study and immersion into Jewish life overseen by a rabbi, a religious panel formally determines that a non-Jewish person has met the requirements for conversion to Judaism by demonstrating a sincere commitment to Jewish beliefs and practices and acceptance of the Jewish community, culture, and history. A formal conversion is also sometimes undertaken by individuals whose Jewish ancestry is questioned or by people who were raised Jewish, but may not actually be considered Jews according to traditional Jewish law.
The procedure and requirements for conversion depend on the sponsoring denomination. A conversion in accordance with the process of a denomination is not a guarantee of recognition by another denomination.
In some cases, a person may forgo a formal conversion to Judaism and adopt some or all beliefs and practices of Judaism. However, without a formal conversion, many highly observant Jews will reject a convert's Jewish status.
There are some groups that have adopted Jewish customs and practices. For example, in Russia the Subbotniks have adopted most aspects of Judaism without formal conversion to Judaism. However, if Subbotniks, or anyone without a formal conversion, wish to marry into a traditional Jewish community or immigrate to Israel, they must have a formal conversion.
A male convert to Judaism is referred to by the Hebrew word ger (Hebrew: גר, plural gerim) and a female convert is a giyoret. The word is rendered by the Greek "proselyte" as used in the Septuagint to denote a "stranger". In Karaite Judaism a Ger is a non-Jew who has yet to fully convert to Judaism. After a Ger converts to Judaism, they are no longer considered a Ger but a full-fledged Jew.