Yom Kippur is a solemn and reflective holiday, so it is not customary to greet those observing with "Happy Yom Kippur". Instead, it is appropriate to greet people warmly when you meet them. Here are some traditional greetings to share:

• Gmar chatima tova: This Hebrew greeting translates to "a good final sealing" in English. It references the traditional belief that a persons fate for the coming year is written on Rosh Hashanah and sealed on Yom Kippur.

• Gmar tov: This is an abbreviated version of "Gmar chatima tova".

• Tzom kal: This Hebrew greeting translates to "easy fast" in English. It is often used in the days preceding the fast or just as its beginning.

• Have an easy fast: This is the English equivalent of "Tzom kal" and is also not uncommon.

• Have a meaningful fast: This greeting recognizes that the purpose of Yom Kippur is not that the fast should be easy per se, but that it should be meaningful.

• Shana tova: This Hebrew greeting translates to "good year" in English and is often used during the Jewish New Year, which comes just a few days before Yom Kippur.

• Chag sameach: This Hebrew greeting translates to "happy holiday" in English and is a generic Jewish holiday greeting that can be used on Yom Kippur.

• Gut yontiff: This Yiddish greeting is a version of the Hebrew phrase "yom tov," which literally means "good day" and refers to any major Jewish holiday on which work is traditionally forbidden.

Remember that Yom Kippur is a time to reflect on the previous year and how to improve for the coming year ahead, so it is appropriate to wish someone a meaningful fast or a good final sealing.