The Greek alphabet has 24 letters, from alpha to omega. To identify one, match its shape and case to the table below, then read its name. Uppercase and lowercase forms belong to the same letter, although they can have different jobs in a formula. Sigma also has a special lowercase form at the end of a Greek word.
This is a reference for recognizing letters in books, notes and technical writing. Knowing that a symbol is called theta helps you name it, but does not tell you what it represents in every equation. For that, you still need the definition supplied by the author.
All 24 Greek letters in order
Read the table downward. The names are conventional English spellings used in references and technical discussion. The Open University alphabet reference supplies both cases and includes final sigma with sigma, rather than giving it a separate alphabet position.
| Uppercase | Lowercase | Name |
|---|---|---|
| Α | α | Alpha |
| Β | β | Beta |
| Γ | γ | Gamma |
| Δ | δ | Delta |
| Ε | ε | Epsilon |
| Ζ | ζ | Zeta |
| Η | η | Eta |
| Θ | θ | Theta |
| Ι | ι | Iota |
| Κ | κ | Kappa |
| Λ | λ | Lambda |
| Μ | μ | Mu |
| Ν | ν | Nu |
| Ξ | ξ | Xi |
| Ο | ο | Omicron |
| Π | π | Pi |
| Ρ | ρ | Rho |
| Σ | σ / ς | Sigma |
| Τ | τ | Tau |
| Υ | υ | Upsilon |
| Φ | φ | Phi |
| Χ | χ | Chi |
| Ψ | ψ | Psi |
| Ω | ω | Omega |
The table contains ordinary Greek text characters, so you can select and copy a letter. Use it as the exact reference; the accompanying study photographs illustrate reading and writing rather than supplying an authoritative alphabet chart. A font may change details of the shapes without changing the letter names.
Why sigma has two lowercase forms
Σ is uppercase sigma. Its lowercase forms are σ and ς. In ordinary Greek words, use σ at the beginning or in the middle and ς at the end. Both lowercase shapes are sigma. Neither the extra shape nor the capital makes sigma more than one of the 24 letters.
In technical notation, σ commonly appears as a standalone symbol. You do not change it into ς merely because it falls at the end of an English sentence or a line of mathematics. The word-final rule describes Greek spelling, not a general instruction to reshape mathematical symbols.
Watch for letters that resemble English letters
Uppercase Ρ looks like an English P, but its name is rho. Η resembles H but is eta, Ν resembles N but is nu, and Χ resembles X but is chi. Υ is upsilon, not the English letter Y. Treat the surrounding script as evidence before deciding which alphabet a shape belongs to.
Lowercase forms can be more revealing. Rho is ρ, eta is η and chi is χ. Nu, ν, can resemble a Latin v in some fonts; lowercase upsilon, υ, can resemble u. Omicron, ο, is easily mistaken for either a Latin o or a zero. If a scan is unclear, check another occurrence and the nearby definitions rather than guessing from one isolated mark.
A letter name does not give a universal technical meaning
The University of Warwick mathematics reference lists examples of how Greek letters are used. Theta often labels an angle; lambda may label an eigenvalue. Those are conventions within a subject, not dictionary definitions that apply every time the letters appear.
For example, θ = 35° can be read as “theta equals thirty-five degrees.” The letter name is theta; the surrounding notation tells you this example concerns an angle. In another passage, an author could define theta differently. Preserve subscripts and other marks when copying it because they may distinguish one quantity from another.
Case matters too. Lowercase σ often represents a population standard deviation, while the related large summation symbol ∑ instructs you to add terms. Our guide to standard deviation explains that statistical use. Recognizing the sigma family is useful, but it does not make these notations interchangeable.
You may also see variant forms such as θ and ϑ for theta, or φ and ϕ for phi. They belong to the same named letter families. In a technical document, however, an author may distinguish variants deliberately. Keep the form used in the source instead of automatically replacing it with the one you prefer.
English technical names and modern Greek pronunciation
Saying the English name of a symbol is a different task from pronouncing a Greek word. English technical discussions use established English letter names, with some regional variation. Modern Greek has its own names and sound patterns. Ancient Greek courses may teach another pronunciation convention again.
A useful example is Β/β. English references call this letter beta, while modern Greek names it vita and uses it for a v sound. The University of Arizona-hosted modern Greek phonetics reference illustrates that distinction. Do not use an English alphabet-name list as a pronunciation key for an entire Greek sentence.
A quick way to check an unfamiliar symbol
First decide whether you are reading a Greek word or technical notation. Next match the shape and case to the table. Write down the name, then return to the sentence, equation legend or definitions to establish its role. If the symbol appears in several places, compare them before treating a blurred stroke as a different letter.
For a personal reference, copy the pairs you regularly confuse onto a spare sheet and keep their names alongside them. You can also browse blank index cards on Amazon for a small set of reusable reference cards. Start with the actual symbols in your reading, and keep recognition separate from interpreting their meaning.
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