Sa is the abbreviation for a word in the Sanskrit language, sadja As it is written in Sanskrit, the's' is pronounced sh. In music, however, it is pronounced s. In music, Sa stands for the syllable, and sadja the word for "the first pitch"; the reason for this divergence in meaning is unknown. Ri (or Re, as it is usually said in the North) is short for risabha, "the second pitch." Ga is short for Gandhara, a word that refers to the area west of the Sindhu River. It is not known why this word is used to refer to a musical pitch. Ma is from madhyama, or "middle"; it refers to the middle pitch in a saptak. Madhyama and the short Hindi form madhya are terms used in several different musical contexts, such as "madhya saptak" (middle register) and "madhya laya" (middle speed). Pa is short for panchama, which means fifth; it is the fifth pitch in a saptak. Dha stands for dhaviat, the sixth pitch. Ni is from Nisada, the name of a non-Aryan tribe in India.
In India, the use of syllables to refer to musical pitches is very old. At some point in time during the Vedic period, roughly around 1500-500 B.C., older names for the pitches were dropped in favour of new ones which are in use now. Yet another source suggests that a solfege system has been mentioned in the Narada Parivajaka Upanishad, dating to around circa 600 B.C. It is also says that in the Kudimiyamalai inscriptions of the Pallava period, sometime in the 7th century A.D., there are whole passages written in sa ri ga ma notation along with vowel variations.
In Carnatic music, the number of pitches available in addition to the basic seven is the same as in Hindustani music. However when they are named, there seems to be more. As seen in the case of Hindustani music, Sa and Pa are invariable. And there are two Mas. However, there are three categories of Ri, Ga, Dha and Ni, unlike in the case of Hindustani music where there are two categories each. The lowest form of each of the variable pitches is considered to be the natural form (suddha). The generic names given to the remaining forms are vikrita svaras.
Pitch in Carnatic music thus plays around the same principles as are observed in the case of Hindustani Classical music.