AUM (also OM)
Hindus usually correct non-Hindu westerners by telling them that the Sankrit word AUM contains three syllables. So, frankly, I’m a bit surprised to see Wikipedia put the “OM” spelling first. ¹
In any case, AUM is a central Hindu mantra. The three syllables (A-U-M) are said to represent three stages of cosmic evolution: Creation (related to the deity Brahma), Sustenance (related to the deity Vishnu) and Destruction (related to the deity Siva).
For correct pronunciation, one begins at the back of the throat (Ah), moves to the middle (OO) and finishes at the exterior of the vocal cavity (MM). Again, this apparently mirrors the mantra’s threefold nature of creation, sustenance and destruction.