Minhag (מנהג "custom", classical pl. מנהגות, modern pl. מנהגים, minhagim) is an accepted tradition or group of traditions in Judaism. A related concept, Nusach (נוסח), refers to the traditional order and form of the prayers.
The Hebrew root N-H-G (נ-ה-ג) means primarily "to drive" or, by extension, "to conduct (oneself)".
The actual word minhag appears twice in the Hebrew Bible; both times in the same verse and translated as "driving":
The watchman reported, saying, "And the watchman told, saying: 'He came even unto them, and cometh not back; and the driving is like the driving of Jehu the son of Nimshi; for he driveth furiously.'"
Homiletically, one could argue that the use of the word minhag in Jewish law reflects its Biblical Hebrew origins as "the (manner of) driving (a chariot)". Whereas Halakha (law), from the word for "walking-path," means the path or road set for the journey, minhag (custom), from the word for driving, means the manner people have developed themselves to travel down that path more quickly.
The present use of minhag for "custom" may have been influenced by the Arabic minhaj; in current Islamic usage, this term is used for the intellectual methodology of a scholar or school of thought (cf. Hebrew derech) rather than for the customs of a local or ethnic community.
In addition to the 613 commandments, Jews have traditionally considered Halacha (Jewish law as derived from the Talmud, responsa literature, Torah, and later codes) binding upon all Jews. In addition to these, there have always been customs and traditions not in the law itself. Some customs were at some points universally adopted (e.g., head-covering among men) or almost universally (e.g., monogamy). Others were or are observed by major segments of Jewry but not by others (e.g., not eating kitniyot on Passover). Other customs are bound to certain localities or groups that originated in certain localities.
These minhagim exist in various forms:
Ancient minhagim go back to the time of the Talmud and earlier.