Vac literally means “to speak,” but to the Vedic Indians, Vac embodies much more than mere speech. Vac is centered around speech as well as song (sung word) in connection with a sense of “calling forth,” of “raising.” Vac has been used to refer to the roaring of animals, the rustling sound of a blazing fire, the sound of flowing Soma (the song that Soma utters), the thundering of the clouds (the sound of Soma pressing stone) and personified in a glorious Goddess, Vac. In short, Vac is the divine embodiment of sound.
Vac is always named in the process of creation, including the creation of the world. She has been noted for her interaction with Sarasvati, Agni, Soma, Prajapati, Brhaspati and Usas. She was created for the performance of sacrifice, and from her sprang forth the Holy mantras, for when her name is added to a prayer, it becomes a charm, a spell. Her presence will transform the words that they may be given to Agni and carried to the Gods. She is said to control the tone, meter and speed of the spoken words as well as their cessation when silence is necessary.
Vac is sometimes looked upon as a cow capable of yielding all desired things equating the powerful and sacred nature of words with the divinely revered animal. She has given the voices to all the creatures, including humans, through her breath.
Pingle, Pratbha M. The Concept of Vac in the Vedic Literature. Sri Satguru Publications, India: 2005. Print.