Feminine words ending in ī and ū which admit the substitute iyaṅ and uvaṅ [[6.1.77]] are not called nadī ; except the word strī (which is called nadī not withstanding its substituting iyaṅ).,
The definition of Nadi given in the last sutra was rather too wide, this limits the scope. Thus श्री, happiness, भ्रू brow, admit the substitutes iyan and uvan respectively, and are not nadi. Their vocative singular is हे श्रीः, हे भ्रूः &c., while the vocative singular of stri is हे स्त्रि.,