Greek numerals in the context of "Tau"

Alpha /ˈælfə/ ALF-ə (uppercase Α, lowercase α) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph ⟨𐤀⟩, whose name comes from the West Semitic word for 'ox'. Letters that arose from alpha include the Latin letter ⟨A⟩ and the Cyrillic letter ⟨А⟩.

Omega (US: /oʊˈmeɪɡə, -ˈmɛɡə, -ˈmiːɡə/ , UK: /ˈoʊmɪɡə/; uppercase Ω, lowercase ω) is the twenty-fourth and last letter in the Greek alphabet. In the Greek numeric system/isopsephy (gematria), it has a value of 800. The name of the letter was originally ὦ (ō̂ [ɔ̂ː]), but it was later changed to ὦ μέγα (ō̂ méga 'big o') in the Middle Ages to distinguish it from omicron ⟨ο⟩, whose name means 'small o', as both letters had come to be pronounced [o]. In modern Greek, its name has fused into ωμέγα (oméga).

In phonetic terms, the Ancient Greek Ω represented a long open-mid back rounded vowel [ɔː], in contrast to omicron, which represented the close-mid back rounded vowel [o], and the digraph ⟨ου⟩, which represented the long close back rounded vowel [uː]. In modern Greek, both omega and omicron represent the mid back rounded vowel [o̞]. The letter omega is transliterated into a Latin-script alphabet as ō or simply o.

Lambda(/ˈlæmdə/ ; uppercase Λ, lowercase λ; Greek: λάμ(β)δα, lám(b)da; Ancient Greek: λά(μ)βδα, lá(m)bda), sometimes rendered lamda, labda or lamma, is the eleventh letter of the Greek alphabet, representing the voiced alveolar lateral approximant IPA: [l]; it derives from the Phoenician letter Lamed, and gave rise to Latin L and Cyrillic El (Л). In the system of Greek numerals, lambda has a value of 30. The ancient grammarians typically called it λάβδα (lắbdă, [lábda]) in Classical Greek times, whereas in Modern Greek it is λάμδα (lámda, [ˈlamða]), while the spelling λάμβδα (lámbda) was used (to varying degrees) throughout the lengthy transition between the two.

In early Greek alphabets, the shape and orientation of lambda varied. Most variants consisted of two straight strokes, one longer than the other, connected at their ends. The angle might be in the upper-left, lower-left ("Western" alphabets) or top ("Eastern" alphabets). Other variants had a vertical line with a horizontal or sloped stroke running to the right. With the general adoption of the Ionic alphabet, Greek settled on an angle at the top; the Romans put the angle at the lower-left.

Delta (/ˈdɛltə/ DEL-tə; uppercase Δ, lowercase δ; Greek: δέλτα, délta, [ˈðelta]) is the fourth letter of the Greek alphabet. In the system of Greek numerals, it has a value of four. It was derived from the Phoenician letter dalet 𐤃. Letters that come from delta include the Latin D and the Cyrillic Д.

A river delta (originally, the delta of the Nile River) is named so because its shape approximates the triangular uppercase letter delta. Contrary to a popular legend, this use of the word delta was not coined by Herodotus.

Pi (/ˈpaɪ/ ; Ancient Greek /piː/ or /peî/, uppercase Π, lowercase π, cursive ϖ; Greek: πι) is the sixteenth letter of the Greek alphabet, representing the voiceless bilabial plosive IPA: [p]. In the system of Greek numerals it has a value of 80. It was derived from the Phoenician letter Pe (). Letters that arose from pi include Latin P, Cyrillic Pe (П, п), Coptic pi (Ⲡ, ⲡ), and Gothic pairthra (𐍀).

Zeta (UK: /ˈziːtə/, US: /ˈzeɪtə/ ; uppercase Ζ, lowercase ζ; Ancient Greek: ζῆτα, Demotic Greek: ζήτα, classical [d͡zɛ̌ːta] or [zdɛ̌ːta] zē̂ta; Modern Greek: [ˈzita] zíta) is the sixth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 7. It was derived from the Phoenician letter zayin . Letters that arose from zeta include the Roman Z and Cyrillic З.

Xi (/zaɪ/ ZY or /(k)saɪ/ (K)SY; uppercase Ξ, lowercase ξ; Greek: ξι) is the fourteenth letter of the Greek alphabet, representing the voiceless consonant cluster [ks]. Its name is pronounced [ksi] https://upload.wikimedia.org/wikipedia/commons/3/3c/De-Xi.ogg in both Ancient Greek and Modern Greek. In the system of Greek numerals, it has a value of 60. Xi was derived from the Phoenician letter samekh .

Xi is distinct from the letter chi, which gave its form to the Latin letter X.

Upsilon (US: /ˈʌpsɪlɒn, ˈ(j)uːp-, -lən/, UK: /(j)uːpˈsaɪlən, ˈʊpsɪlɒn/ ; uppercase Υ, lowercase υ; Greek: ύψιλον ýpsilon [ˈipsilon]) or ypsilon /ɪp-/ is the twentieth letter of the Greek alphabet. In the system of Greek numerals, Υʹ has a value of 400. It is derived from the Phoenician waw .

Psi /ˈ(p)saɪ, ˈ(p)siː/ (P)SY, (P)SEE (uppercase Ψ, lowercase ψ or 𝛙; Greek: ψι psi [ˈpsi]) is the twenty-third and penultimate letter of the Greek alphabet and is associated with a numeric value of 700. In both Classical and Modern Greek, the letter indicates the combination /ps/ (as in English word "lapse").

For Greek loanwords in Latin and modern languages with Latin alphabets, psi is usually transliterated as "ps".