A sentence which is a means of valid knowledge is called verbal testimony. It is the fourth kind of valid knowledge in Nyaya philosophy, it is called Sabda or agama orauthoritative verbal testimony. Its means is called Sabda. It is defined as the statement of a trustworthy person (aptavakya) and consists in understanding its meaning. A sentence is defined as a collection of words and a word is defined as that which is potent to convey its meaning. The power in a word to convey its meaning comes, according to ancient Nyaya, from God, and according to later Nyaya, from long established convention.
