<P> Letter frequencies, like word frequencies, tend to vary, both by writer and by subject . One cannot write an essay about x-rays without using frequent Xs, and the essay will have an idiosyncratic letter frequency if the essay is about the frequent use of x-rays to treat zebras in Qatar . Different authors have habits which can be reflected in their use of letters . Hemingway's writing style, for example, is visibly different from Faulkner's . Letter, bigram, trigram, word frequencies, word length, and sentence length can be calculated for specific authors, and used to prove or disprove authorship of texts, even for authors whose styles are not so divergent . </P> <P> Accurate average letter frequencies can only be gleaned by analyzing a large amount of representative text . With the availability of modern computing and collections of large text corpora, such calculations are easily made . Examples can be drawn from a variety of sources (press reporting, religious texts, scientific texts and general fiction) and there are differences especially for general fiction with the position of' h' and' i', with H becoming more common . </P> <P> Herbert S. Zim, in his classic introductory cryptography text "Codes and Secret Writing", gives the English letter frequency sequence as "ETAON RISHD LFCMU GYPWB VKJXQ Z", the most common letter pairs as "TH HE AN RE ER IN ON AT ND ST ES EN OF TE ED OR TI HI AS TO", and the most common doubled letters as "LL EE SS OO TT FF RR NN PP CC". </P> <P> Also, to note that different dialects of a language will also affect a letter's frequency . For example, an author in the United States would produce something in which the letter' z' is more common than an author in the United Kingdom writing on the same topic: words like "analyze", "apologize", and "recognize" contain the letter in American English, whereas the same words are spelled "analyse", "apologise", and "recognise" in British English . This would highly affect the frequency of the letter' z' as it is a rarely used letter elsewhere in the English language . </P>

Letters of the alphabet in order of usage