question: what determines the popular letters in latin style-languages?
comment: from my understanding, it's about how latin mixed with the local writing system. for example, the sound made by the letters "ae" in latin (pronounced like eye in english) would be spelled differently in different regions due to pre-existing alphabets and accents.
passages: Depending on the language, some letter-diacritic combinations may be considered distinct letters, e.g. for the purposes of lexical sorting. This is the case, for example, of Romanian "ș" () and Spanish "ñ" ().
  
  The following are the most common use of diacritics in Romance languages.
   In the course of its use, the Latin alphabet was adapted for use in new languages, sometimes representing phonemes not found in languages that were already written with the Roman characters. To represent these new sounds, extensions were therefore created, be it by adding diacritics to existing letters, by joining multiple letters together to make ligatures, by creating completely new forms, or by assigning a special function to pairs or triplets of letters. These new forms are given a place in the alphabet by defining an alphabetical order or collation sequence, which can vary with the particular language.
   The term "Latin alphabet" may refer to either the alphabet used to write Latin (as described in this article) or other alphabets based on the Latin script, which is the basic set of letters common to the various alphabets descended from the classical Latin alphabet, such as the English alphabet. These Latin-script alphabets may discard letters, like the Rotokas alphabet or add new letters, like the Danish and Norwegian alphabets. Letter shapes have evolved over the centuries, including the development in Medieval Latin of lower-case, forms which did not exist in the Classical period alphabet. English is the only major modern European language requiring no diacritics for native words (although a diaeresis may be used in words such as "coöperation").
   Latin spelling, or Latin orthography, is the spelling of Latin words written in the scripts of all historical phases of Latin from Old Latin to the present. All scripts use the same alphabet, but conventional spellings may vary from phase to phase. The Roman alphabet, or Latin alphabet, was adapted from the Old Italic script to represent the phonemes of the Latin language. The Old Italic script had in turn been borrowed from the Greek alphabet, itself adapted from the Phoenician alphabet. The Latin alphabet most resembles the Greek alphabet around 540 BC, as it appears on the black-figure pottery of the time.
   Section::::Writing systems.:Diacritics.
  
  Romance languages also introduced various marks (diacritics) that may be attached to some letters, for various purposes. In some cases, diacritics are used as an alternative to digraphs and trigraphs; namely to represent a larger number of sounds than would be possible with the basic alphabet, or to distinguish between sounds that were previously written the same. Diacritics are also used to mark word stress, to indicate exceptional pronunciation of letters in certain words, and to distinguish words with same pronunciation (homophones).
   Section::::Letterforms.
  
  The forms of the Latin alphabet used during the Classical period did not distinguish between upper case and lower case. Roman inscriptions typically use Roman square capitals, which resemble modern capitals, and handwritten text often uses old Roman cursive, which includes letterforms similar to modern lowercase.
  
  This article uses small caps for Latin text, representing Roman square capitals, and long vowels are marked with acutes, representing apices. In the tables below, Latin letters and digraphs are paired with the phonemes they usually represent in the International Phonetic Alphabet.
  
  Section::::Letters and phonemes.
   While most of the 23 basic Latin letters have maintained their phonetic value, for some of them it has diverged considerably; and the new letters added since the Middle Ages have been put to different uses in different scripts. Some letters, notably "H" and "Q", have been variously combined in digraphs or trigraphs (see below) to represent phonetic phenomena that could not be recorded with the basic Latin alphabet, or to get around previously established spelling conventions. Most languages added auxiliary marks (diacritics) to some letters, for these and other purposes.
   With the fragmentation of political power, the style of writing changed and varied greatly throughout the Middle Ages, even after the invention of the printing press. Early deviations from the classical forms were the uncial script, a development of the Old Roman cursive, and various so-called minuscule scripts that developed from New Roman cursive, of which the Carolingian minuscule was the most influential, introducing the lower case forms of the letters, as well as other writing conventions that have since become standard.
   No exact letter frequency distribution underlies a given language, since all writers write slightly differently. However, most languages have a characteristic distribution which is strongly apparent in longer texts. Even language changes as extreme as from old English to modern English (regarded as mutually unintelligible) show strong trends in related letter frequencies: over a small sample of Biblical passages, from most frequent to least frequent, enaid sorhm tgþlwu (æ)cfy ðbpxz of old English compares to eotha sinrd luymw fgcbp kvjqxz of modern English, with the most extreme differences concerning letterforms not shared.
   Section::::Writing systems.:Upper and lower case.
  
  Most languages are written with a mixture of two distinct but phonetically identical variants or "cases" of the alphabet: majuscule ("uppercase" or "capital letters"), derived from Roman stone-carved letter shapes, and minuscule ("lowercase"), derived from Carolingian writing and Medieval quill pen handwriting which were later adapted by printers in the fifteenth and sixteenth centuries.
   Section::::Key types of differences.
  
  Apart from alphabets for modern spoken languages, there exist phonetic alphabets and spelling alphabets in use derived from Latin script letters. Historical languages may also have used (or are now studied using) alphabets that are derived but still distinct from those of classical Latin and their modern forms (if any).
  
  The Latin script was typically slightly altered to function as an alphabet for each different language (or other use), although the main letters are largely the same. A few general classes of alteration cover many particular cases: 
  
  BULLET::::- diacritics could be added to existing letters;
   In Livonian, whose alphabet is based on a mixture of Latvian and Estonian alphabets, the comma is used on the letters "ḑ", "ļ", "ņ", "ŗ", "ț" to indicate palatalization in the same fashion as Latvian, except that Livonian uses "ḑ" and "ț" represent the same palatal plosive phonemes which Latvian writes as "ģ" and "ķ" respectively.
   Otherwise, letters that are not combined as digraphs generally represent the same phonemes as suggested by the International Phonetic Alphabet (IPA), whose design was, in fact, greatly influenced by Romance spelling systems.
  
  Section::::Writing systems.:Digraphs and trigraphs.
   Section::::As used by various languages.:Letters.
  
  Some examples of new letters to the standard Latin alphabet are the Runic letters wynn and thorn , and the letter eth , which were added to the alphabet of Old English. Another Irish letter, the insular "g", developed into yogh , used in Middle English. Wynn was later replaced with the new letter , eth and thorn with , and yogh with . Although the four are no longer part of the English or Irish alphabets, eth and thorn are still used in the modern Icelandic and Faroese alphabets.
   BULLET::::11. Catalan also has a large number of digraphs: "dj, gu, gü, ig, ix, ll, l·l, ny, qu, qü, rr, ss, tg, tj, ts, tx, tz". The letters "K", "Ñ", "Q" "W", and "Y" are only used in loanwords or the digraphs mentioned.
  
  BULLET::::12. ↑ Chamorro also has the digraphs "ch, ng". "C" used only in digraphs.
  
  BULLET::::13. ↑ Corsican has the trigraphs: "chj, ghj".
   Since most Romance languages have more sounds than can be accommodated in the Roman Latin alphabet they all resort to the use of digraphs and trigraphs – combinations of two or three letters with a single phonemic value. The concept (but not the actual combinations) is derived from Classical Latin, which used, for example, "TH", "PH", and "CH" when transliterating the Greek letters "θ", "ϕ" (later "φ"), and "χ". These were once aspirated sounds in Greek before changing to corresponding fricatives, and the "H" represented what sounded to the Romans like an following , , and respectively. Some of the digraphs used in modern scripts are:
   Some adaptations of the Latin alphabet are augmented with ligatures, such as æ in Danish and Icelandic and Ȣ in Algonquian; by borrowings from other alphabets, such as the thorn þ in Old English and Icelandic, which came from the Futhark runes; and by modifying existing letters, such as the eth ð of Old English and Icelandic, which is a modified "d". Other alphabets only use a subset of the Latin alphabet, such as Hawaiian, and Italian, which uses the letters "j, k, x, y" and "w" only in foreign words.
   BULLET::::- Front rounded vowels are present in all four branches. usually fronts to , and secondary mid front rounded vowels often develop from long or .
  
  BULLET::::- Extreme lenition (i.e. multiple rounds of lenition) occurs in many languages especially in Langue d'oïl and many Gallo-Italian languages.
  
  BULLET::::- The Langue d'oïl, Swiss Rhaeto-Romance languages and many of the northern dialects of Occitan have a secondary palatalization of and before , producing different results from the primary Romance palatalization: e.g. "centum" "hundred"  "cent" , "cantum" "song"  "chant" .
   These often were given a place in the alphabet by defining an alphabetical order or collation sequence, which can vary between languages. Some of the results, especially from just adding diacritics, were not considered distinct letters for this purpose. For example, the French é and the German ö are not listed separately in their respective alphabet sequences. Digraphs in some languages may be separately included in the collation sequence (e.g. Hungarian CS, Welsh RH). New letters must be unless collation is not practised.
  
  Section::::Properties.
  
  Section::::Properties.:Letter inventory.
  
  Coverage of the letters of the ISO basic Latin alphabet can be
  
  BULLET::::- complete
   BULLET::::- In Portuguese, the collating order is just like in English: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z. Digraphs and letters with diacritics are not included in the alphabet.
  
  BULLET::::- In Romanian, special characters derived from the Latin alphabet are collated after their originals: A, Ă, Â, ..., I, Î, ..., S, Ș, T, Ț, ..., Z.
   Section::::Summary of evolution.
  
  The Latin alphabet started out as uppercase serifed letters known as roman square capitals. The lowercase letters evolved through cursive styles that developed to adapt the formerly inscribed alphabet to being written with a pen. Throughout the ages, many dissimilar stylistic variations of each letter have evolved that are still identified as being the same letter.
   The Romance languages are written with the classical Latin alphabet of 23 letters – "A", "B", "C", "D", "E", "F", "G", "H", "I", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "V", "X", "Y", "Z" – subsequently modified and augmented in various ways. In particular, the single Latin letter "V" split into "V" (consonant) and "U" (vowel), and the letter "I" split into "I" and "J". The Latin letter "K" and the new letter "W", which came to be widely used in Germanic languages, are seldom used in most Romance languages – mostly for unassimilated foreign names and words. Indeed, in Italian prose is properly . Catalan eschews importation of "foreign" letters more than most languages. Thus Wikipedia is in Catalan but in Spanish.
   Section::::History.:Classical Latin alphabet.
  
  After the Roman conquest of Greece in the 1st century BC, Latin adopted the Greek letters and (or readopted, in the latter case) to write Greek loanwords, placing them at the end of the alphabet. An attempt by the emperor Claudius to introduce three additional letters did not last. Thus it was during the classical Latin period that the Latin alphabet contained 23 letters:
  
  Section::::History.:ISO basic Latin alphabet.
   The spelling rules of most Romance languages are fairly simple, and consistent within any language. Since the spelling systems are based on phonemic structures rather than phonetics, however, the actual pronunciation of what is represented in standard orthography can be subject to considerable regional variation, as well as to allophonic differentiation by position in the word or utterance. Among the letters representing the most conspicuous phonological variations, between Romance languages or with respect to Latin, are the following:
   In addition to representing the respective vowels and , and also typically represent the semivowels and , respectively, when unstressed and occurring before another vowel. Many exceptions exist (e.g. , , , , , , , , , , , ). Unstressed may represent that a preceding or following or is 'soft' ().
  
  Section::::C and G.
  
  Normally, and represent the plosives and , respectively, unless they precede a front vowel ( or ) when they represent the affricates (like English "ch") and (like English "j").
  