Shabda Pramana in Hinduism is a term used by grammarians to refer to a linguistic evidence. This unit can be a word or a sentence; hence Shabhda can be used with reference to a word or a sentence when conceived as an integral unit. This Shabda (or the meaning-bearing unit) is called sphota by grammarians. Thus, at different levels, we can have the word sphota as the sentence or sphota as the shabda.
Patanjali defines Shabda as that which when uttered conveys the idea of the referent or the thing meant. Mandana Mishra in his Sphota Siddhi defines Shabda as that which produces the idea of the object.
According to sphota theory of Bhartrhari, the complete utterance of the sentence, taken as an integral meaning-bearing unit, is the vakya-sphota. At a lower level, the word could also be considered as a unit, pada sphota. Of course, in common parlance, even an utterance can be called shabda.
According to the Mimamsa School of philosophy, Shabda is a phonemic pattern, a series of articulated phonemes in a particular order of sequence. The linguistic unit is the varna (phoneme); a collection of varna in a particular series conveys the meaning. This school declares that shabda is momentary, lasting only for a moment; both the grammarians and the Mimamsakas declare that the Shabda is a permanent relationship between Shabda and artha.
Linguistic behavior in this world is possible only because of the innate and permanent relation between a word and its meaning. Though the word may be a unit of language, the unit of speech is the sentence. Bhartrhari held the view that the vakya sphota is the real unit of speech, and that the word, the root suffix, etc., are the result of linguistic analysis and that such an analysis has only a pragmatic value.
Shabda, or language as an independent means of valid knowledge, has been discussed by different schools of thought in India. The Buddhists and Vaiseshikas include it under inference; the validity of a sentence depends on the reliability of the speaker. The Mimamsakas, who consider Vedic injunctions as reliable, believe that Vedic texts are free from the defects of the author, since they are impersonal and eternal. The Naiyayikas take them as the word of God and hence reliable.