Orthographies that use alphabets and syllabaries are based on the principle that the written symbols (graphemes) correspond to units of sound of the spoken language: phonemes in the former case, and syllables in the latter. However, in virtually all cases, this correspondence is not exact. Different languages' orthographies offer different degrees of correspondence between spelling and pronunciation. English orthography, French orthography and Danish orthography, for example, are highly irregular, whereas the orthographies of languages such as Russian, German and Spanish represent pronunciation much more faithfully, although the correspondence between letters and phonemes is still not exact. Finnish, Turkish and Serbo-Croatian orthographies are remarkably consistent: approximation of the principle "one letter per sound".