Vriddhi is the eleventh nityayoga, and its name means growth, increase, and prosperity. It is one of the auspicious yogas, favourable for undertakings meant to expand and flourish, new ventures, investments, and matters of increase. Like every nityayoga it is found from the combined longitude of Sun and Moon divided into twenty-seven equal parts, advancing through the month. In the panchanga it contributes its favourable, expansive quality to the reckoning of an auspicious time, one of the five daily limbs the tradition weighs. These are the conventions of the calendar tradition, in which a benefic yoga such as Vriddhi commends a moment for growth; the astronomical basis remains the simple arithmetic of the two luminaries' summed longitude.
Vriddhi, growth or increase, is also a specific technical term in Sanskrit grammar, naming one of the two regular categories of vowel strengthening, vriddhi and guna, that Panini's grammatical system uses to describe how a root vowel changes in forming derived words, so the same word that names this auspicious yoga also names a foundational concept in the analysis of the Sanskrit language itself. The yoga's calendrical sense of growth and prosperity and the grammatical sense of a strengthened vowel are independent developments of the same basic root meaning, augmentation or increase, rather than one being derived from the other.