In Hinduism, Shiva, the third deity in the Hindu Trinity responsible for the transformation of the universe at the end of a cycle of creation, is revered in both anthropomorphic and Shivling forms. The latter, however, is the more common, with the former being an exception. Immovable Shivling worshipped in a temple is known as Achalalinga (or Acalalinga).
Shivlings can be chala (movable) or achala (immovable). The
achalalingas, also known as sthavara-lingas, are stone lingas permanently
installed in temples. They come in various classifications, organized into
four, six, or even nine groups.
An achalalinga comprises three parts: Brahmabhaga (square in
shape), Viishnubhaga (octagonal), and Rudrabhaga (round). The first two parts
are embedded within the pedestal, while only the third part is visible. This
visible part, known as the ‘pujabhaga,’ is the focal point of worship or puja.
Etymologically, the term ‘linga’ signifies that in which
everything dissolves (liyate asmin iti lingaแธฅ). Additionally, ‘linga’ also
denotes an emblem. Therefore, the Shivling serves as an emblem of God Shiva,
representing the dissolution of everything during the destruction of the
created universe. As God transcends name and form, and our understanding of
abstract principles like Him relies on concrete symbols, a rounded surface
serves as a fitting approximation.