Goddess Annapurna is regarded as the deity of nourishment. The term Anna denotes grains or food and Purna means complete or full in Sanskrit. Goddess Annapurna is the incarnation of Goddess Parvati. Worshipping of annadhana (food) and the offering of food is much revered and respected in Hindu religion and therefore Annapurna Puja is one of the significant rituals in Hindu mythology.
Devotees recite the Annapurna Sahasranama in order to worship the Goddess and her 108 names are also recited while chanting the Annapurna Shatanama Stotram.
Annapurna Puja is observed on the eighth day (Ashtami) of the religious festival of Navratri and a lot many devotees break their fast on this particular day.
To please the Goddess, the devotees prepare and offer a bhog (sacred food) of Puri, Halwa and Kala Chana to the deity and seek her blessings.
According to the legend, Goddess Parvati was told by Lord Shiva that everything in the universe is an illusion i.e. Maya and food is one of them. Goddess Parvati who is signified as the deity of all materialistic things comprising food got angry.
In order to show the actual significance and importance of the materialistic things, the deity disappeared from the universe. As a result of her disappearance everything went to a standstill and the entire earth became barren. All the beings started suffering from hunger as there was no food available anywhere. By seeing all the sufferings and pain, Goddess Parvati incarnated in Kashi and set up a kitchen.
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Knowing about the return of the Goddess, Lord Shiva rephrased his saying and told her that he had realized the importance of material world, it is a spirit which cannot be just dismissed like an illusion. Goddess Parvati smiled and fed Lord Shiva by her own hands. Since that time period, Goddess Parvati is also worshipped as Goddess Annapurna and a grand Annapurna Puja is performed in order to please the deity of Nourishment.