A bar mitzvah is (1) a 13-year-old Jewish boy who has assumed full religious obligations, and (2) the coming-of-age ceremony that recognizes a 13-year-old Jewish boy as a bar mitzvah. Bat mitzvah is the corresponding term for females. In Hebrew, mitzvah means commandment, bar means son, and bat means daughter. The terms do not need to be capitalized or italicized.
Mizvah is a variant of mitzvah, but it appears only rarely in modern writing.
In the following examples, bar mitzvah applies to a coming-of-age ceremony for a Jewish boy:
Jon Zobel turned $500 in bar mitzvah money into $2,000 by buying and flipping limited-edition shoes. [Miami Herald]
I made my debut with the camera at an evening bar mitzvah for Alex, one of my son’s friends. [Financial Times]
And in these examples, bat mitzvah applies to a ceremony for a girl:
My sister is supposed to be studying for her bat mitzvah in July. [Toronto Sun]
Deborah (not her real name) has celebrated her bat mitzvah, graduated from eighth grade, and has participated in overnight adventures alongside her peers. [Jewish United Fund]