Final answer:
Rosh Chodesh is the Jewish term for the beginning of a new lunar month and holds significance in the setting of dates for Jewish holidays, notably embodied in the Passover narrative.
Step-by-step explanation:
Rosh Chodesh, which means 'head of the month' in Hebrew, is the term used to denote the beginning of a new lunar month in the Jewish calendar. The importance of lunar months in Judaism is evident in their language with regards to timekeeping; 'yerach' meaning month in biblical Hebrew and 'chodesh' stemming from 'new', reflecting the practice of measuring time from one new moon to the next. This system of timekeeping is significant in various cultural and religious practices, including the setting of dates for Jewish holidays such as Passover, a festival that involves the ritual meal known as the Seder, commemorating the Exodus from Egypt and emphasizing the importance of the lunar calendar in Jewish tradition.