Why do we use the word mantram instead of mantra?
All of Dr. Bormann's research on the Mantram Repetition Program originates from the work of Eknath Easwaran who founded the Blue Mountain Center of Meditation in Tomales, CA. The guidelines for how to use a mantram in the West were first introduced by Easwaran in the 1960's. He was raised in south India in Kerala and learned mantram repetition from his grandmother.
When Sanskrit words are spoken without being embedded in a Sanskrit sentence, they are often left in their stem form; that is, they are not declined. Many words have a "stem" form that just ends in "a" as in "yoga" "deva" and "mantra". When speaking in Sanskrit, an unembedded word is often declined in either nominative (mantraH) or accusative (mantram). Thus, "mantram" is the accusative case of the masculine word "mantra" and declining it in this way is one way of using the word outside of a sentence when in a formal Sanskrit context.
A special thanks to John D. Dunne for this second explanation.
Associate Professor Department of Religion Emory University