What does the Sanskrit word "Amavasya" signify in Hindu religion?

Amavasya (Sanskrit: अमावस्या) is the lunar phase of the New Moon in Sanskrit. Indian calendars use 30 lunar phases, called tithi (duration of two faces of moon observed from earth) in India. The dark moon tithi is when the moon is within 12 degrees of the angular distance between the sun and the moon before conjunction (union). The New Moon tithi (the first day in the lunar fortnight) is the 12 angular degrees after conjunction.

On this day, the moonlight is absent because the sun and the moon are in the same direction as seen from the earth. Scientifically, Amavasya is the lunar phase of the New Moon. The night of Amavasya comes after every 30 days, it can be said that Amavasya comes once a month.

Many festivals, the most famous being Diwali (the festival of lights), are observed on Amavasya. Many Hindus fast on Amavasya. Every month, the day of Amavasya is considered auspicious to worship forefathers, and pujas ( worship rituals) are organised for offering oblations to departed ancestors. People also take a holy dip in river Ganga on Amavasya day. Amavasya which falls on Mondays has its special significance in Hindu religion. It is believed that observing fast on this day would ward off widowhood in women and ensure the bearing of progeny. It is highly auspicious to offer food, clothes and footwears to a brahmin or priest.