Om Shanti Shanti Shanti

Oṃ śānti śānti śānti.

Pronunciation notes:

• o is pronounced like o in ore
• ā is pronounced as a in father
• i in speech is pronounced like i in mill, but in chanting is pronounced like ee in bee

Om (Oṃ)

Like many mantras, this one begins with "Om". Om has no meaning, and its origins are lost in the mists of time. Om is considered to be the primeval sound, the sound of the universe, the sound from which all other sounds are formed.

In the Brahminical tradition, from where Buddhism undoubtedly obtained mantra practice, Om is not just the universal sound, but the sound of the universe itself. For example in the (non-Buddhist) Mandukya Upanishad, it is said:

Om! — This syllable is this whole world.

Its further explanation is: –

The past, the present, the future — everything is just the word Om.

And whatever else that transcends threefold time — that, too, is just the word Om.

Om is therefore a sound symbolizing reality. It represents everything in the universe, past, present, and future. It even represents everything that is outside of those three times. It therefore represents both the mundane world of time in which the mind normally functions, and the world as perceived by the mind that is awakened and that experiences the world timelessly. It represents both enlightenment and non-enlightenment.

You could regard Om as being the equivalent of white light, in which all of the colors of the rainbow can be found.

One Sanskrit-English dictionary says the following:

"A word of solemn affirmation and respectful assent , sometimes translated by ‘yes, verily, so be it’ (and in this sense compared with Amen); it is placed at the commencement of most Hindu works, and as a sacred exclamation may be uttered at the beginning and end of a reading of the Vedas or previously to any prayer; it is also regarded as a particle of auspicious salutation [Hail!];

Om appears first in the Upanishads as a mystic monosyllable, and is there set forth as the object of profound religious meditation, the highest spiritual efficacy being attributed not only to the whole word but also to the three sounds A, U, M, of which it consists."

*In Om shanti, ‘Om’ means myself i.e. in Sanskrit ‘Aham’ and ‘Shanti’ refers to Peace. Om Shanti is saying "I am a peaceful soul."

Shanti (Śānti)

Shanti (Pali: Santi) simply means "peace". It’s a beautiful meaning and also a very beautiful sound. The shanti is repeated three times, as are many chants in Buddhism. In Buddhism as well as in Hinduism the threefold Shanti is generally interpreted as meaning the Threefold Peace in body, speech, and mind (i.e. peace in the entirety of one’s being).

Hindu teachings typically end with the words Om shanti shanti shanti as an invocation of peace, and the mantra is also used to conclude some Buddhist devotional ceremonies.

Śānti, or inner peace, arises when the mind has let go of both grasping and aversion. For this reason the Buddhist path of practice is known in Pali as "santimagga" (Sanskrit: śāntimarga) or The Path of Peace, as expressed in the famous Dhammapada verse, "Santimaggam eva brūhaya" — Cultivate this very Path of Peace.

In conclusion, at the end of Yoga when your instructor says Om Shanti Shanti Shanti you are saying: I am a peaceful soul: Peace in words, deeds and thoughts which leads to peace and happiness.

Each Shanti is praying for a specific thing: Here we go into the first, second and third shanti:

Shanti is chanted thrice not for emphasis but because disturbances are of three distinct categories. In Sanskrit, these are referred to as adhi-daivikam, adhi-bhautikam and adhyatmikam.

Adhi-daivikam literally means "mental disturbances that come from God"—i.e. things that are utterly beyond our control: hurricanes, earthquakes, volcanic eruptions, floods, tsunamis, etc. We have no control over these types of disturbances. So when we say the first shanti, we are praying, "O God, may we be protected from these obstacles that are beyond our control."

Adhi-bhautikam literally means "disturbances that come from the world." That means anything stemming from the world around us—mosquitoes, noisy neighbors, barking dogs, the phone ringing, family arguments. As opposed to the first category, we have some control over this second category of disturbances. We can use mosquito repellent, we can call the police on our neighbors, we can turn off the phone, we can leave the place altogether, etc. So this shanti means, "O God, may we be protected from the people and surroundings."

The third type of disturbance is the most powerful and, at the same time, the only one over which we have total control. Adhyatmikam means "disturbances stemming from the self." For one who is still identified with the ego, the people, places and things of this world stimulate one of two reactions in the mind—attachment or aversion. Whether we physical see someone we consider our enemy as we walk down the street or remember him during meditation, the mental turbulence that results is the same. Lust, jealousy, anger, sorrow, hatred destroy our peace. During meditation, pleasant memories also distract us. Hearing the sound of a jet plane flying overhead may mentally carry us off to a fabulous holiday we once took. Only after 10 minutes of daydreaming do we realize we have lost focus on our object of meditation.

In fact, Amma says that the ego is the only true obstacle to mental peace. This third shanti is therefore the most important one, because even if we are free from outside disturbances, if the inner realm is not calm we will never know peace. Conversely, once we have found inner peace, no external force can ever disturb us. So chanting this third shanti is akin to praying, "O God, please remove all the inner obstacles."

There is one more element to the three-fold chanting of "shanti," and that is the silence that follows each repetition. If chanted properly, this silence is the emphasis: shanti... shanti.... shanti....
This silence is representative of true peace, the peace of an Enlightened One like Amma. For the spiritual seeker, peace is the goal. For an Enlightened One peace has been realized as his very nature. To have be have equipoise in every situation in life verily is realization.

So I did some research of classic yoga chants and mantras and I found this one that I really love:

OM SAHANA VAVATU SAHANA BHUNATTU
SAHA VIRYAM KARAWAVAHAI
TEJASVINAVADITAMASTU
MA VIDVISHAVAHAI
OM SHANTI SHANTI SHANTI OM

Together may be be protected
Together may we be nourished
Together may we work with great energy
May our journey together be brilliant and effective
May there be no bad feelings between us
Peace, peace, peace

(From the Kato Upanishad)

information, thanks to:

http://www.wildmind.org/mantras/figures/shanti

http://archives.amritapuri.org/bharat/mantra/shanti.php