Grantha Letter Dha

It is Grantha dha, a consonant letter used to write Sanskrit.

Grantha developed from Brahmi. Intermediate Grantha forms appear in early Pallava inscriptions from the fourth century; the modern form represented here belongs to the tradition after the thirteenth century. Grantha gave Sanskrit writers voiced and aspirated consonants that Tamil writing represented less directly.

Grantha appears beside Tamil in bilingual inscriptions and mixed commentary manuscripts. A related Grantha tradition also helped shape modern Malayalam; that script history explains the connection without making this letter Tamil or Malayalam.

Why does its shape change in a word?

Its built-in vowel and cluster partners shape the syllable. A Grantha consonant carries a built-in 'a' vowel until a vowel sign changes it; the virama suppresses that vowel.

In a consonant cluster, the virama may join the preceding consonant into a ligature. Grantha clusters can also appear as stacked letters.

Fonts may show 𑌧 alone, in a compact ligature, or inside a taller stack. Manuscripts also preserve archaic ligatures unlike contemporary print; these are shaping and historical-style differences, not changes in character identity.