In Sanskrit grammar, one of the three grades of the verb stem. The zero grade is shortest, guna is of middle length, and vrddhi is the longest form of the stem vowel.

Short a becomes long â in vrddhi, i becomes ai (with intermediate guna e), and u becomes au (with guna o). The syllabic consonants r and l acquire a long â.

The name comes from the root vrdh, meaning grow.