Vrittis are powers of words to convey meaning. Sri Madhvacharya has put forward a new vritti and it is known as paramamukhya vritti. As per Madhwa School, paramamukhya vritti is of two kinds – mahayoga and mahayogarudhi.
Factors that are responsible for using words to convey things are called pravritti nimitta. Independent authority is one such factor.
A king is described as victorious when his army achieves a victory. Here the supreme authority of the king is responsible for such a statement. Here the vritti of the word is mahayoga. The presence of attributes in things in an infinite measure is another factor. The word purusha denoted parabrahman. The word means the above virtues. There are there in Him in an infinite measure. Here the vritti is mahayoga. In addition to this factor, if a word is widely used to denote a being, the vritti is mahayogarudhi. The word Narayana denotes Parabrahman by this vritti.
The words which denote deficiencies and weaknesses in persons or things do denote Parabrahman also by mahayoga, as He presides over these verities also.
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Generally, Vrittis are powers of words to convey meaning. Shakti, which denotes primary, and lakshana, which conveys secondary meanings are known as vrittis. Rudhi, yoga, and yogarudhi come under sakti vrittis. These are sufficient to accommodate the Vedic assertions mentioned above.
Source - Notes taken from Encyclopedia of Hinduism Volume III - page 559 - IHRF - Rupa - 2011