Vahana or vahanam denotes the being, typically an animal or mythical entity, a particular Hindu deity is said to use as a vehicle. In this capacity, the vahana is often called the deity's "mount". Upon the partnership between the deity and his vahana is woven much iconography and Hindu theology. Deities are often depicted riding the vahana. Other times, the vahana is depicted at the deity's side or symbolically represented as a divine attribute. The vahana may be considered an accoutrement of the deity: though the vahana may act independently, they are still functionally emblematic or even syntagmatic of their "rider". The deity may be seen sitting or standing on the vahana. They may be sitting on a small platform, or riding on a saddle or bareback.
The eight Matrikas riding different vahanas like (top row, second from left to right) Garuda, a peacock, Nandi bull, a hamsa (goose/swan); (bottom row, from left) buffalo, elephant and lion
Image: Thajavur Ganesha
Image: Suryatanjore
Image: Garuda by Hyougushi in Delhi
Nandi, also known as Nandikeshvara or Nandideva, is the bull vahana (mount) of the Hindu god Shiva. He is also the guardian deity of Kailash, the abode of Shiva. Almost all Shiva temples display stone images of a seated Nandi, generally facing the main shrine.
Nandi in a zoo-anthropomorphic form
Nandi - Shiva's bull in front of Hindu temple, Rewalsar, HP, India
Decorated Nandhi at temple in Thanjavur
2nd-century CE sculpture of a Nandi in Mysore