The affix dhā comes after a prātipadika (Nominal Stem) denoting a Numeral when it means the mode or manner of an action.,
The word विधा and प्रकार have the same meaning. The adverbs so formed apply to every kind of action. Thus एकधा भुङ्क्ते 'he eats once'. द्विधा गच्छति 'he goes twice'. Similarly त्रिधा, चतुर्धा, पञ्चधा ॥,