Siddham letter ṭha

It writes ṭha: a curled-back “t” with a puff of air.

By itself, 𑖙 is the syllable ṭha, including an inherent “a.” A vowel sign changes that vowel; the virama 𑖿 removes it, and consonants can join in a conjunct. In bonji-input, .th is the input sequence for the ṭh consonant.

How did Siddham travel with Buddhist texts?

Buddhist teaching carried the script across Asia.

A teaching object from Sugh dated to the second or first century BCE preserves the older Brahmi letter order Siddham later inherited; it does not show this later glyph. The recognizable Siddham form, also called Siddhamātr̥kā, took shape in northern India in the second half of the first millennium. Central Asian fragments from the sixth to tenth centuries preserve syllable charts and student exercises.

Siddham developed through the Brahmi–Gupta stream of northern Indian scripts. It is closely related to Sharada and connected with Devanagari and other northern scripts. It served to write and teach Sanskrit; Buddhist transmission carried it to China, Korea, and Japan for Buddhist texts, including mantras, dhāraṇīs (long Buddhist formulas), and sutras. In Japan, it became especially associated with Shingon and Tendai rites. Its ordered alphabet also influenced Japanese kana charts, tables that arrange Japanese syllabic writing.

Why does Siddham change shape or disappear on screen?

A font controls the shape, and some fonts lack Siddham coverage.

The displayed form can vary with font and regional tradition. If the font has no Siddham glyph, the character may appear as an empty box; a Siddham font such as Noto Sans Siddham may provide coverage.