U03C4

U03C4 is the Unicode codepoint designation for the Greek small letter tau. Its official name in the Unicode Standard is “Greek small letter tau.” The codepoint value is U+03C4, and it is represented in hexadecimal as 0x03C4. In UTF‑8 encoding, U+03C4 is encoded as the three‑byte sequence E1 80 94. In typical Latin‑based typefaces, the lowercase tau resembles a lowercase letter ‘t’ with a tail that extends below the baseline.

The phonetic value of the Greek letter tau is the voiceless alveolar plosive sound [t], similar to the English letter “t.” In classical Greek, tau served as the t‑consonant in the Greek alphabet. It is the 19th letter in the Greek ordering and has a corresponding uppercase form, T (U+03A4). Greek dialects such as Koine and Modern Greek use tau in the same letter form.

In mathematical and scientific contexts, the lowercase tau (τ) appears frequently. It is often used as a variable representing time, torsion, or a transmission ratio. In geometry, the Greek letter tau has received attention as a constant equal to 2π (tau constant), advocating a more natural representation of circle geometry than π. The symbol also appears in physics to denote relaxation time, shear stress, and tunneling probability, among other quantities.

Beyond mathematics, τ is used in linguistics to indicate the target language in the comparative method and in biology to denote specific transcription factors. In computing, the Unicode character U+03C4 is widely supported across major operating systems and terminals, facilitating correct rendering in web pages, documents, and software that support Unicode.