Shanti means peace. Generally after saying prayers one says Om Shantihi, Shantihi, Shantihi. Shanti is said thrice to express an intense desire for peace and to be liberated from misery and obstacles. All sorrows and pain come from three sources : adhidaivika, adhibhautika and adhyatmika.
1. Adhidaivika means the operation of natural forces by devas which are responsible for earthquakes, floods, famine, volcanic eruptions and other natural calamities. They are all due to displeasure of the devas (nature gods) towards mankind.
2. Adhibhautika due to animals and man. The latter creates war, pollution and performs crime and other painful and cruel acts.
3. Adhyatmika is created because of the mental state and attitudes like anger, frustration , etc.
The devout pray to god to free them from such problems or obstacles in their daily work or special tasks. Therefore the word Shantihi is chanted thrice. The first address the unseen forces of devas the second Shantihi is chanted softer and directed towards man and the surrounding circumstances and the final Shantihi is chanted the softest because it is addressed directly to one’s own mind.