Observe Yom Kippur is a Jewish holiday that is observed by fasting and atoning for sins. It is a day of reflection and repentance, and is one of the most important holidays in the Jewish faith. To observe Yom Kippur, one must FAST and ATONE, which can be done by saying prayers and performing acts of charity. The term ATONE, which has five letters, refers to making amends for wrongs committed, while FAST, which has four letters, refers to abstaining from food and drink for a period of time.