The Ninth Night - Why not 10 or 11 0r 8?

Divine Nine
For nine days and nights we have celebrated the triumph of the Goddess over evil.
Navaratri.
Why nine, you might ask?
Why not 11 or 8 or any other number for that matter?
Well, maybe because nine is quite a number, it seems!
The “Complete” number
From the vantage point of pure mathematics - and we Indians are somewhat of an authority on the subject - the number 9 is considered to be a complete or “puran” number. Why? Because do anything to this number and it remains unchanged, unaffected, like Devi Herself. Multiply 9 by any number and the answer always totals to 9. Add it to or subtract it from any number, the answer always totals to the number or the sum of the one that you added or subtracted, nine remaining serenely untouched, unmoving.
23 x 9 = 207
74 x 9 = 576
5 + 9 = 14
25 + 9 = 34
87 – 9 = 78
13 – 9 = 4
This concept is explained in the Upanishads.
The primordial, celestial number
A human being spends 9 months in its mother’s womb before it is born. At the rate of 15 breaths a minute, a healthy human being takes an average of 21600 breaths in 24 hours or 9 x 100 breaths in an hour!
The number nine also leaps up and strides across the heavens - in the form of the 9 celestial bodies or the Navagraha. Planets, would you say? Well, I don’t really know because only 6 of the planets in the Western or solar system of astronomy figure in the navagrahas. Also by the Western system, the Sun is a star, and Rahu and Ketu aren’t planets at all. And the earth, Pluto and Neptune don’t figure at all which should leave us serenely unaffected by all the recent teeth-gnashing about that poor lil’ dwarf, Pluto!
Sun (Surya),
Moon (Chandra),
Mars (Mangal/Bhaum),
Mercury (Budha),
Jupiter (Guru/Bruhaspati),
Venus (Shukra)
Saturn (Shani)
Rahu and
Ketu.
Also, the navagrahas aren’t considered just planets, but also divine entities to be both worshipped and appeased. Surya, for example is the son of sage Kasyapa and Aditi, while Shani is Surya’s son. Chandra (the moon) is a Deva who took the 27 (9x3!) stars (Nakshatras and daughters of Daksha) as his wives. Bruhaspati (Jupiter) was the teacher of devas, a mighty scholar whose utterances made it into every branch of Indian philosophy. Budha (Mercury) is considered the son of Chandradeva while Sukra (Venus) is a benign deva so wealthy that all the precious stones are in his possession and Kubera lives by constantly borrowing a quarter of his wealth from Sukra!
The Ecologically Correct Number
The navagraha puja gave rise to the concept of navadhaanya or the 9 sacred seeds or grains offered to each of the 9 grahas. And if we look at them beyond just offerings in a ritual, we see the embodiment of life itself and what the principle of what now an eco-fashionable word – biodiversity. Because these 9 seeds and grains are the perfect balance of cereal (wheat and rice), legume (Bengal gram, green gram, horse gram, black gram and red gram) and nuts/oilseed (sesame) which is the principle behind crop rotation in agriculture, now making a “comeback” among agriculturists as one of the most powerful and enduring ways to enrich and rejuvenate the soil.
The divine number
So, I guess the Devi picked the right number, don’t you think?
And nine has a special significance for the Devi in other ways.
In Bengal, during Durga Puja, a special Devi is made out of 9 plants called nabapatrika. Each plant represents one avatar of the Devi - the banana plant for Goddess Brahmani, the colacassia or arvi plant for Kalika, turmeric for Durga, jayanti denotes Kartiki, bel or bilva (wood apple) for Goddess Shiva, pomegranate for Raktadantika, the ashoka tree for Sokrahita, arum for Chamunda and finally rice for Goddess Lakshmi.
Every one of those plants are nutritionally and/or medicinally potent!
But the ultimate divine significance of this number is in the fact that across all religions, the name of God is invoked in multiples of 9. The japamala or prayer beads used by Hindus, Jains and Buddhists has 108 beads. (The Buddhists believe that the 108 beads represent the number of mental conditions or sinful desires that one must overcome to reach enlightenment or nirvana.) The Quran list 99 names of Allah and so the Muslim prayer beads known as the tasbeeh usually has sets of 99 counting beads for each of the names and one elongated terminal bead. The Jains chant the panchanamaskara in multiples of 9. And in Christianity, the word “novena” itself is from the Latin word “novem” or 9 and so this prayer is chanted in sets of 9 – 9 consecutive hours, days, even weeks or months.
The number of life
Finally, let us come a full circle – literally - and rest where we began. With mathematics. Or with the meaning of life itself, depending on how you want to look at it. We talk about the circle of life. The zero as well as the wheel is a circle, without which much of what we call civilization or progress, would not have happened or existed. All the planets including the sun, moon and the one that we live on are, when viewed in one dimension - a circle. And the circle is the ultimate symbol of infinity – that which has no beginning and no end. So then consider this – in geometry, the number of degrees that make up a circle are 360.
Or 9 x 40!
Source material: Puranic Encyclopedia by Vettam Mani