Teth, also written as Ṭēth or Tet, is the ninth letter of the Semitic abjads, including Phoenician ṭēt 𐤈, Hebrew, Aramaic ṭēṯ 𐡈, and Syriac ṭēṯ ܛ, and Arabic ṭāʾ ط‎. It is also related to the Ancient North Arabian 𐪗‎‎‎, South Arabian 𐩷, and Geʽez ጠ.

The Phoenician letter also gave rise to the Greek theta (Θ), originally an aspirated voiceless dental stop but now used for the voiceless dental fricative. The Arabic letter (ط) is sometimes transliterated as Tah in English, for example in Arabic script in Unicode.

The sound value of Teth is /tˤ/, one of the Semitic emphatic consonants.

The Phoenician letter name ṭēth may mean "spinning wheel" pictured as (compare Hebrew root ט-ו-י‎ (ṭ-w-y) meaning 'spinning' (a thread) which begins with Teth). According to another hypothesis (Brian Colless^{[citation needed]}), the letter possibly continues a Middle Bronze Age glyph named ṭab 'good', Aramaic טַב‎ 'tav', Hebrew טוב‎ 'tov', Syriac ܛܒܐ 'tava', modern Arabic طَيّب 'ṭayyib', all of identical meaning.

Jewish religious books about the "holy letters" from the 10th century onward discuss the connection or origin of the letter Teth with the word tov "good". This is alluded to in a cryptic aggadata in the Talmud Baba Kamma 54b. Additionally the first time the letter "tes" appears in the Torah is in the word "Tov" meaning "good." This was especially emphasized ever since the late 1600s after the Baal Shem Tov became influential, since the letter Teth was in his Acronym standing for Tov, and goodness was part of his philosophy. The acrostic poems of the Bible use 'Tov' to represent the letter (e.g. Psalm 119:65-72).

The letter is named ṭāʾ  طَاءْ; Modern Standard Arabic pronunciation: /tˤ/.

It has four forms, and the letter does not change its shape depending on its position in the word:

The Hebrew spelling of name of the letter: טֵית‎