Estonian orthography is essentially phonemic with each phoneme of the language represented by exactly one grapheme. Exceptions to this derive from historical agreements: 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 very 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.
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. Another influence that had persisted in the 20th century and beyond is using a spaced em dash — which is often used in professional publications (books, etc), although many Estonian computer users not knowledgable in correct orthography tend to use a hyphen-minus, a figure dash or an en dash instead, with no spacing or with variable spacing.
It should be noted than Estonian words and names quoted from Soviet sources are often incorrect back-transliterations from the Russian transliteration. Examples are the use of "ya" for "ä" (e.g. Pyarnu instead of the correct Pärnu) and "y" instead of "õ" (e.g., Pylva instead of the correct Põlva).