The official Estonian alphabet has 27 letters: A, B, D, E, F, G, H, I, J, K, L, M, N, O, P, R, S, Š, Z, Ž, T, U, V, Õ, Ä, Ö, Ü.
Occasionally, the alphabet is recited without them, and thus has only 23 letters: A, B, D, E, G, H, I, J, K, L, M, N, O, P, R, S, T, U, V, Õ, Ä, Ö, Ü. Additionally C, Q, W, X, and Y are used in writing foreign proper names.
Double letters are used to write half-long and overlong vowels and consonants, e. g. aa [ɑː] or [ɑːː], nn [nː] or [nːː], kk [kːː].
As the distinction between voiced and voiceless plosives is not native to Estonian, the names of the letters 'b', 'd', 'g' may be pronounced [peːː], [teːː], [keːː], so the letters 'b' and 'd' are also named nõrk B (weak B) and nõrk D (weak D) to distinguish them from tugev P (strong P) and tugev T (strong T).
Although the Estonian orthography is generally guided by phonemic principles, with each grapheme corresponding to one phoneme, there are some historical and morphological deviations from this: for example the initial letter 'h' in words, preservation of the morpheme in declension of the word (writing b, g, d in places where p, k, t is pronounced) and in the use of 'i' and 'j'.
Where it is impractical or impossible to type š and ž, they are substituted with sh and zh in some written texts, although this is considered incorrect.
Otherwise, the h in sh represents a voiceless glottal fricative, as in Pasha (pas-ha); this also applies to some foreign names.
Some features of the modern Estonian orthography are: One consonant between two vowels belongs to the following syllable: kala 'fish' is syllabified ka-la.
However, a hiatus is formed in morpheme bounds, e. g. avaus 'opening' is syllabified a-va-us as the word is composed from the root ava- and the suffix -us.
Foreign proper names from Latin-script languages are written in their original spelling: Margaret Thatcher, Bordeaux.
Names from non-Latin-script languages are written using either Estonian orthographic transcription or established romanization systems.
Names of months, days of the week, holidays, Chinese zodiac years, and titles of people such as professor are not capitalized.
For case endings beginning with the letter l, the hyphen is mandatory to avoid confusion with the digit 1: 16-le for kuueteistkümnele 'sixteen [allative]'.
The quotation marks, written as „ ”, are used for direct speech, citations, scare quotes, and names of books, documents, episodes, enterprises, etc.
Names of plant sorts may be written in double or in single quotation marks (looking like apostrophes: ’ ’) and are normally italicized.
Sometimes the apostrophe is used for adding case endings and suffixes to Estonian names, to make the original form clear: Metsa’le (allative of the surname Metsa), mutt’lik (the apostrophe is used to conserve the spelling of the surname Mutt, otherwise the double consonant would become a single consonant).
The square brackets are used for citer's notes to citations and for showing pronunciation in linguistic and reference works.
The slash is used for division in fractions and unit symbols, for connecting alternatives, to show line breaks when citing poetry in the single-line format, and for non-calendar years.
Before Otto Wilhelm Masing introduced the letter õ in the early 19th century, its sound had not been distinguished in writing from ö.
In Fraktur typesetting (which was common in Estonian publications before the first half of the 20th century), two kinds of the small letter s were distinguished: the short s and the long ſ.
Estonian words and names quoted in international publications from Soviet sources were often back-transliterations from the Russian transliteration.
Examples are the use of я ("ya") for ä (e.g. Pyarnu (Пярну) for Pärnu), ы ("y") for õ (e.g., Pylva (Пылва) for Põlva) and ю ("yu") for ü (e.g., Pyussi (Пюсси) for Püssi).