Estonian orthography is the system used for writing the Estonian language and is based on the Latin alphabet. The Estonian orthography is generally guided by phonemic principles, with each grapheme corresponding to one phoneme.
Due to German and Swedish influence, the Estonian alphabet (Estonian: eesti tähestik) has the letters Ä, Ö, and Ü (A, O, and U with umlaut), which represent the vowel sounds [æ], [ø] and [y], respectively. Unlike the German umlauts, they are considered and alphabetised as separate letters and are part of the alphabet. The most distinctive letter in the Estonian alphabet, however, is the Õ (O with tilde), which was added to the alphabet in the 19th century by Otto Wilhelm Masing and stands for the vowel [?]. In addition, the alphabet also differs from the Latin alphabet by the addition of the letters ? and ? (S and Z with caron/há?ek), and by the position of Z in the alphabet: it has been moved from the end to between S and T (or ? and ?).
The official Estonian alphabet has 27 letters: A, B, D, E, F, G, H, I, J, K, L, M, N, O, P, R, S, ?, Z, ?, T, U, V, Õ, Ä, Ö, Ü. The letters F, ?, Z, ? are so-called "foreign letters" (võõrtähed), and occur only in loanwords and foreign proper names. 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. They do not occur in Estonian words, and are not officially part of the alphabet. Including all the foreign letters, the alphabet consists of the following 32 letters:
|C||c||[ts]||[tse:]||Not officially part of the alphabet; only used in loanwords|
|F||f||[f]||[ef?]||Only used in loanwords|
|H||h||[h], [?], [ç] or [x]||[h?:] or [h]|
|K||k||[k] or [k:]||[k?:]|
|P||p||[p] or [p:]||[pe:]|
|Q||q||[k]||[ku:]||Not officially part of the alphabet; only used in loanwords|
|?||?||[?]||[:]||Only used in loanwords|
|Z||z||[z]||[zet?] or [ze:]||Only used in loanwords|
|?||?||[?]||[?e:]||Only used in loanwords|
|W||w||[?]||[k?k.sis'?e:]||Not officially part of the alphabet; only used in loanwords|
|X||x||[ks]||[iks]||Not officially part of the alphabet; only used in loanwords|
|Y||y||[i]||[i?.rek] or [yp.si.lon]||Not officially part of the alphabet; only used in loanwords|
In Blackletter script W was used instead of V.
Johannes Aavik suggested that the letter Ü be replaced by Y, as it has been in the Finnish alphabet.
|aa||[?:] or [?::]|
|ee||[e:] or [e::]|
|ii||[i:] or [i::]|
|oo||[o:] or [o::]|
|uu||[u:] or [u::]|
|õõ||[?:] or [?::]|
|ää||[æ:] or [æ::]|
|öö||[ø:] or [ø::]|
|üü||[y:] or [y::]|
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[clarification needed], 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'.[clarification needed] Where it is impractical or impossible to type ? and ?, 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.
Modern Estonian orthography is based on the Newer Orthography created by Eduard Ahrens in the second half of the 19th century based on Finnish orthography. The Older Orthography it replaced was created in the 17th century by Bengt Gottfried Forselius and Johann Hornung based on standard German orthography. Earlier writing in Estonian had by and large used an ad hoc orthography based on Latin and Middle Low German orthography. Some influences of the standard German orthography -- for example, writing 'W'/'w' instead of 'V'/'v' persisted well into the 1930s.
Estonian words and names quoted in international publications from Soviet sources are often back-transliterations from the Russian transliteration. Examples are the use of ? ("ya") for ä (e.g. Pyarnu () for Pärnu), ? ("y") for õ (e.g., Pylva () for Põlva) and ? ("yu") for ü (e.g., Pyussi () for Püssi). Even in the Encyclopædia Britannica one can find "ostrov Khiuma", where "ostrov" means "island" in Russian and "Khiuma" is back-transliteration from Russian instead of "Hiiumaa" (Hiiumaa > (?) > Khiuma).