अदेङ् गुणः

Each one of the letters अ, ए and ओ whether radical or secondary is called a guna letter; as the initial vowels in the following:- अर्त्ति,\he moves\; एति \he comes\, ओखति \he goes.\ Here the initial vowels of the roots ऋ, इ, and उख् have been respectively gunated into अर्, ए, and ओ before the third person singular termination ति.

The term Guna occurs in sutras like मिदेर्गुणः 7.3.82. \Let there be guna substitute for the ik of the root मिद् \to melt.\,