Amavasya is a Sanskrit term that refers to the lunar phase of the new moon. It is often translated as "no moon day" or "new moon day" in English. During this phase, the Moon is within 12 degrees of the Sun and is not visible in the sky. Indian calendars use 30 lunar phases, called tithi in India, and the dark moon tithi is considered Amavasya.

In Hinduism, Amavasya is considered a time of great power and is observed as an auspicious day for the worship of forefathers. Many Hindus fast on Amavasya, and festivals such as Diwali, the festival of lights, are observed on this day. In Tamil, Amavasya is commonly referred to as Amavasai in religious spheres, but pure Tamil scholars prefer the term Puthuppi Rai.

According to Sadhguru, a spiritual leader, Amavasya means "no moon day" or "new moon day" and is a time when something or somebody becomes absent, and through that absence, their presence becomes more powerful. On this day, there is a certain integration of the elements, and everything slows down. If one is seeking liberation, Amavasya is considered sacred.

In summary, Amavasya is the lunar phase of the new moon and is considered a time of great power in Hinduism. It is observed as an auspicious day for the worship of forefathers, and many Hindus fast on this day. According to Sadhguru, Amavasya is a time when something or somebody becomes absent, and through that absence, their presence becomes more powerful.