Au (Indic)

Definition
Au is a vowel character in the family of Indic abugidas. It appears both as an independent letter and as a vowel sign that modifies a base consonant in scripts derived from ancient Brahmi.

Overview
In modern Indic writing systems, the vowel Au represents the diphthong /au/ (often transcribed as “au” in IAST). It is used across a wide range of South‑Asian languages that employ Brahmic scripts, including Hindi, Sanskrit, Bengali, Gujarati, Malayalam, Odia, Telugu, and several others. The independent form of Au is employed when a syllable begins with the vowel sound, while the dependent vowel sign attaches to a consonant to replace its inherent “a” vowel.

Etymology / Origin
The glyph for Au traces its lineage to the middle “Kushana” period of the Brahmi script (circa 1st–3rd centuries CE) and later to the Gupta script. Early Brahmi did not possess a distinct Au character; it emerged in more flowing Brahmi variants and was subsequently standardized in the Kushana and Gupta alphabets. The Brahmi form of Au is believed to have been derived from the letter O, which itself likely originated from the Aramaic Waw, linking it historically to the Latin letters F, V, U, W, Y and the Greek upsilon (Υ).

Characteristics

• Phonemic representation: Typically realized as the diphthong /au/ (e.g., [aʊ] or [ɔː] in various languages).
• Forms:
  1. Independent vowel – a standalone glyph (e.g., Devanagari औ, Bengali ঔ, Gujarati ઔ).
  2. Vowel sign – a diacritic attached to a consonant (e.g., Devanagari ौ, Bengali ৌ).
• Script‑specific shapes: While the underlying phonetic value is consistent, the visual shape of Au varies markedly among scripts (e.g., the rounded form in Malayalam ഔ versus the angular form in Devanagari औ).
• Numerical use: In the Āryabhaṭa numeration system, the Au vowel sign (॔) multiplied a consonant’s numeric value by 10¹⁶, though the independent vowel itself held no intrinsic numeric value.
• Historical variants: Apart from Brahmi, Au also appears in related scripts such as Kharoṣṭhī (where it is expressed by adding vowel marks to the independent vowel A) and Tocharian (derived directly from Brahmi).

Related Topics

• Indic abugida – the writing system family to which Au belongs.
• Brahmi script – the ancestral script from which Au and other Indic letters evolved.
• Vowel signs – diacritic forms used in Brahmic scripts to alter the inherent vowel of consonants.
• Āryabhaṭa numeration – an ancient Indian numeral system employing letters, including Au, for numeric values.
• Specific script articles – e.g., Au (Devanagari), Au (Bengali), Au (Gujarati), each detailing script‑specific usage and orthography.