Silent letter

In an alphabetic writing system, a silent letter is a letter that, in a particular word, does not correspond to any sound in the word's pronunciation. In linguistics, a silent letter is often symbolised with a null sign . Null is an unpronounced or unwritten segment. The symbol resembles the Scandinavian letter Ø and other symbols.
English.
One of the noted difficulties of English spelling is a high number of silent letters. Edward Carney distinguishes different kinds of "silent" letters, which present differing degrees of difficulty to readers.
The distinction between "endocentric" digraphs and empty letters is somewhat arbitrary. For example, in such words as "little" and "bottle", one might view as an "endocentric" digraph for , or view as an empty letter; similarly, with or in "buy" and "build".
Not all silent letters are completely redundant:
Silent letters arise in several ways:
Since accent and pronunciation differ, letters may be silent for some speakers, but not others. In non-rhotic accents, is silent in such words as "hard", "feathered"; in "h"-dropping accents, is silent. A speaker may or may not pronounce in "often", the first in "Antarctic", in "sandwich", etc.
Differences between British English and American English.
Pronunciation.
In the US, the "h" in "herb" is silent ("an herb"), but in the UK, it is pronounced ("a herb"). The same is true for the "l" in "solder".
In parts of the UK, the "a" in "dictionary" and "secretary" is silent, but in the US, it is pronounced.
Spelling.
In US spellings, silent letters are sometimes omitted (e.g., "acknowledgment" / UK "acknowledgement", "ax" / UK "axe, "catalog" / UK "catalogue, "program" / UK "programme outside computer contexts), but not always (e.g., "dialogue is the standard spelling in the US and the UK; "dialog" is regarded as a US variant; the spelling "axe" is also often used in the US). In most words, silent letters are written in both styles (e.g., "debt", "guard", "house").
Other Germanic languages.
Danish.
The Danish language has different letters that can be silent.
The letter is silent in the conjuction "af".
The letter is silent in the conjuctions "og" and "også".
The letter is silent in most dialects if followed by , as in "hvad" (‘what’), "hvem" (‘who’), "hvor" (‘where’).
The letter is silent at the end of words if preceded by , as in "selv" ('self'), "halv" ('half').
The letter is usually (but not necessarily) silent if preceded by a consonant, as in "en mand" (‘a man’), "blind" (‘blind’). Many words ending in are pronounced with a stød, but it is still considered a silent letter.
Faroese.
The Faroese language has two silent letters.
The letter is almost always silent. It is rendered in orthography for historical reasons (e.g. 'father' , cf. Old Norse ). In some cases, however, the letter is pronounced , as in 'the weather' .
The letter (i.e. continuant of Old Norse ) is usually silent between vowels or when following a vowel before a pause (e.g. 'day' , cf. Old Norse ; 'I' , cf. Old Norse ). Use of the silent letter in Faroese is the same as for the letter "edd" - it is written for historical reasons as Faroese orthography was based on normalised spelling of Old Norse and Icelandic language.
Both Faroese silent letters and are replaced by a hiatus glide consonant (, or ) when followed by another (unstressed) vowel.
German.
In German, silent letters are extremely rare and occur usually in loanwords, rather than German words.
The long sound is sometimes written , with a silent , as in "Wien" ('Vienna') or in the verb ending (e.g. "appellieren, organisieren").
In some words of foreign origin, the after is pronounced, e.g. "Ambiente, "Bakterien" (plural of "Bakterium"), Hygiene, Klient", "Spermien" (plural of "Spermium"), but is silent in e.g. "Kurier, Papier, Turnier" and all the "-ieren" verbs already mentioned. In "Zeremonie", the final is usually silent but always pronounced in its plural form "Zeremonien".
Words ending in can be somewhat tricky to learners: 
For example, the final is pronounced in the words "Akazie, "Aktie, "Aktinie, "Begonie, "Familie, "Folie, "Geranie, "Grazie, "Hortensie, "Hostie, "Immobilie, "Kastanie, "Komödie, "Kurie, "Lilie, "Linie, "Orgie, "Pinie, "Serie, "Studie, "Tragödie", 
while it is silent in the words "Akademie, "Allergie, "Amnesie, "Amnestie, "Apathie, "Artillerie, "Batterie,"Blasphemie, "Chemie, "Chirurgie, "Demokratie, "Energie, "Epidemie, "-gamie, "Garantie, "Genie, "Geometrie, "-grafie/-graphie, "Harmonie, "Hysterie, "Infanterie, "Ironie, "Kavallerie, "Knie, "Kompanie, "Kopie, "-logie, "Liturgie, "Magie, "Manie, "Melodie, "Monotonie, "Nostalgie, "Orthopädie, "Partie, "Phantasie, "Philantropie, "Philatelie, "Philosophie, "Poesie (but the "e" after the "o" is pronounced), "Psychiatrie, "Rhapsodie, "Sinfonie, "-skopie, "Theorie, "Therapie, "Utopie".
In the female names "Amalie, "Emilie, "Otilie, "Zäzilie, the final e is pronounced, but it is silent in "Leonie, "Marie (but in compound words such as "Marienplatz" [a place in Munich], "Marienstatue" [statue of the Virgin Mary], the e is pronounced; the Virgin Mary is called "Maria" in German), "Nat(h)alie, "Rosalie, "Rosemarie, "Stefanie (or: "Stephanie), "Valerie.
The e is pronounced in the names "Ariel(le)", "Daniel","Daniela", "Gabriel", "Gabriel(l)e (in "Gabriele, the final e is pronounced), "Gabriella", "Mariele (the final e is pronounced), "Mariella", "Muriel,", but it is silent in "Dieter", "Frieda", "Friederich", "Siegfried", "Siegrid", "Sieglinde (the final e is pronounced), "Wieland".
In country names ending in "-ien" , the e is pronounced: "Australien", "Brasilien", "Indien", "Kroatien", "Serbien", "Slowenien".
In city names, the pronunciation of "e" after "i" varies: In "Wien" (Vienna), the e is silent, but in "Triest", it is pronounced.
A silent "h" sometimes indicates vowel length, as in "Stuhl" ('chair'), or a hiatus, as in "drehen" ('to turn'). That "h" derives from an old in some words such as "sehen" ('to see') "zehn" ('ten'), but in other words, it has no etymological justification such as "gehen" ('to go') or "mahlen" ('to mill').
Romance languages.
French.
Silent letters are common in French, including the last letter of most words. Ignoring auxiliary letters that create digraphs (such as , , , , , , and , and and as signals for nasalized vowels), they include almost every possible letter except and .
Vowels.
Final is silent or at least (in poetry and song) a nearly-silent schwa ; it allows the preservation of a preceding consonant, often allowing the preservation of a grammatical distinction between masculine and feminine forms in writing, e.g., in "vert" and "verte" (both ‘green’); the is pronounced in the latter (feminine) but not the former. Furthermore, the schwa can prevent an awkward ending of a word ending in a consonant and a liquid ("peuple, sucre").
After , , or , a final is silent. The spelling is pronounced just the same as that for and is entirely an etymological distinction, so in that context, the is silent.
After or , is almost always silent.
Consonants.
In most dialects, the letter is almost always silent, except in the digraphs and . However, in some words, an initial letter marks an audible hiatus that prevents liaison, cf. words starting with an aspirated h. Numerous doubled consonants exist; French does not distinguish doubled consonants from single consonants in pronunciation as Italian does. A marked distinction exists between a single and doubled : doubled is always voiceless , while an intervocalic single is voiced .
The nasal consonants and when final or preceding a consonant ordinarily nasalize a preceding vowel but are not themselves pronounced ("faim", "tomber", "vin", "vendre"). Initial and intervocalic and , even before a final silent , are pronounced: "aimer", "jaune".
Most final consonants are silent, usual exceptions to be found with the letters , , , and (the English word careful is mnemonic for this set). But even this rule has its exceptions: final is usually pronounced /e/ (=) rather than the expected /ɛʀ/. Final is silent after even in a diphthong ("œil", "appareil", "travail"). Final -"ent" is silent as a third-person plural verb ending, though it is pronounced in other cases.
Final consonants that might be silent in other contexts (finally or before another consonant) may seem to reappear in pronunciation in liaison: "ils ont" "they have", as opposed to "ils sont" "they are"; liaison is the retention (between words in certain syntactic relationships) of a historical sound otherwise lost, and often has grammatical or lexical significance.
Italian.
The letter most often marks a / as hard (velar), as in "spaghetti", where it would otherwise be soft (palatal), as in "cello", because of a following front vowel ( or ). Conversely, a silent marks a / as soft where it would otherwise be hard because of a following back vowel (, , or ), as in "ciao", "Perugia". 
Silent is also used in forms of the verb "avere" ('have') – "ho", "hai" and "hanno" – to distinguish these from their homophones "o" ('or'), "ai" ('to the') and "anno" ('year'). The letter is also silent at the beginning of words borrowed from other languages, such as "hotel".
Spanish.
Despite being rather phonemic, Spanish orthography retains some silent letters:
Greek.
In the Greek language the comma also functions as a silent letter in a handful of Greek words, principally distinguishing ("ó,ti", "whatever") from ("óti", "that").
Slavic languages.
Czech.
In the vast majority of cases, Czech pronunciation follows the spelling. There are only four exceptions:
D
For example: dcera (daughter) and in srdce (heart)
/j/ + consonant clusters in some words.
In most present forms of the verb "být" ("to be"), namely "jsem", "jsi", "jsme", "jste" and "jsou" (i.e. all persons but the 3rd person singular "je"), the initial cluster /js/ is regularly simplified to a mere /s/. This pronunciation is considered correct and neutral when the verb is unstressed and used as an auxiliary. When stressed or used lexically, only the full /js/ pronunciation is considered correct. In casual speech, however, a few other highly frequent words commonly undergo similar simplification, namely all present forms of "jít "("to walk") beginning with /jd/ (that is "jdu", "jdeš", "jde", "jdeme", "jdete", "jdou"), the noun "jméno" ("name") and the verb "jmenovat (se)" ("to name, to ("be") call("ed")").
Russian.
Several words in Russian omit written consonants when spoken. For example, "чувствовать" (chuvstvovat') is pronounced [ˈt͡ɕustvəvətʲ] and "солнце" (solntse) is pronounced [ˈsont͡sə].
Russian letter ъ has no phonetic value and functions as a separation sign. Before the spelling reform of 1918 this hard sign was written at the end of each word when following a non-palatal consonant.
Semitic languages.
In Hebrew language, almost all cases of silent letters are silent aleph – א. Many words that have a silent aleph in Hebrew, have an equivalent word in Arabic language, that is written with a mater lectionis alif –ا ; a letter that indicates the long vowel "aa". Examples:
The explanation for this phenomenon is that the Hebrew language had a sound change of all the mater lectionis aleph letters into silent ones (see Canaanite shift). Due to that sound change, in Hebrew language, there are only two kinds of aleph - the glottal stop (/ʔ/) and the silent one, while in Arabic language all three kinds still exist.
The silent Arabic alif is marked with a wasla sign above it (see picture), in order to differentiate it from the other kinds of alifs. An Arabic alif turns silent, if it fulfils three conditions: it must be in a beginning of a word, the word must not be the first one of the sentence, and the word must belong to one of the following groups:
Besides the alif of the Arabic word ال (ʔal, meaning "the"), its lām (the letter L) can also get silent. It gets silent if the noun that word is related to, starts with a "sun letter". A sun letter is a letter that indicates a consonant that is produced by stopping the air in the front part of the mouth (not including the consonant M). The Hebrew equivalent to the Arabic word ال (ʔal, meaning "the") had totally lost its L.
In Maltese għ can be silent e.g. għar - meaning cave - and pronounced "ahr", or a voiced HH if it is followed by the or if it is at the end of a word e.g. qlugħ (q-glottal stop: qluh).
Uralic languages.
The Estonian and Finnish languages use double letters for long vowels and geminate consonants.
Turkish.
In the Turkish language, often has no sound of its own, but lengthens the preceding vowel, for example in "dağ" ("mountain") . In other surroundings, it may be pronounced as a glide.
Indic languages.
Unconventional to Sanskrit and Proto-Indo-European root languages, some Indic languages have silent letters. Among Dravidian languages, Tamil and Malayalam have certain distinct styles of keeping few of their letters silent.
Tamil.
Tamil is a classical language phonetically characterized by allophones, approximants, nasals and glottalised sounds. Some words, however, have silent letters in them. The words அஃது (while that is), and அஃதன் (that) contain the "Āytam" or ", which is not pronounced in Modern Tamil. It is explained in the "Tolkāppiyam" that "āytam" could have the glottalised the sounds it was combined with, though some may argue it sounded more like the Arabic " (). That being said, modern words like ஆஃபிஸ் (Office) use " and " in sequence to represent the sound, as the "āytam" is nowadays also used to transcribe it and other foreign phonemes.
Another convention in Middle Tamil (Sen-Tamil) is the use of silent vowels to address a mark of respect when beginning proper nouns. The Ramayana was one such text where the word "Ramayana" in Tamil always began with ", as in இராமாயணம் (), though it was not pronounced. The name கோபாலன் () was so written as உகோபாலன் prefixed with an ".
Malayalam.
Malayalam is a Sanskritized language in which speakers always pronounce all letters. The only known exception for consonants in the language is നന്ദി (, thank you), where " () is never pronounced.
Inheriting elision, approximants and allophones from Tamil, in Malayalam, except for Sanskrit words, words ending in the vowel " () become silent at the end and if not compounded with words succeeding them, replace the " vowel by the schwa . However, it is considered disrespectful to change this pronunciation in the simple present verbs, when using imperatives and using what can be termed as Imperative-Active voice in Malayalam, where the second person is respectfully addressed with his or her name instead of നീ (, you) or നിങ്ങൽ (, yourselves). For example, in the sentence, രാകേശ് പണി തീർക്കു (, Rakesh, finish your work), the use of the second personal pronoun is avoided with the name രാകേശ് (, Rakesh), but this sentence sounds less respectful if the " in തീർക്കു (, finish} is replaced by the schwa or , as in "തീർക്കു!" (, Finish!) which sounds like an order. Notice the at the end of the name Rakesh which is pronounced after being added to the Sanskritic name.
Zhuang-Tai languages.
Thai.
Thai has a deep orthography like English and French. Unlike the two languages, however, the Thai script is an abugida rather than a true alphabet. Nonetheless, silent consonants, vowels, and even syllables are common in Thai. Thai has many loanwords from Sanskrit and Pali, and rather than spell aforementioned words according to Thai phonics, the script tends to maintain the etymological spellings. For example, the word ประโยชน์ would be spelled in romanization as "prayochṅ", but it would be pronounced as "prayot", where the extra letter for "-n" is completely silent. Also, the Thai word มนตร์ is written as "mantra" like it would be in Sanskrit, but it is only pronounced "mon" in Thai. Though the second syllable is pronounced in Sanskrit, it is completely absent when pronouncing the word in Thai.
Also, different letters can be used for the same sound (for example, [tʰ] can be spelled as ฐ,ฑ,ฒ,ถ,ท, or ธ) depending on which class the consonant is, which is important for knowing which tone the syllable will have, and whether or not it is a loanword from Sanskrit or Pali. However, some letters written before low class consonants become silent and turn the low class syllable into a high class one. For example, even though the high class letter "ho hip" ห is used to write the sound /h/, if the letter comes before a low class letter in a syllable, the letter will become "ho nam," which will make the letter silent and it will turn the syllable into a high class syllable. For example, the word นา is a low class syllable because its initial consonant is a low class consonant. The syllable is pronounced "nā:" (with a long vowel and mid tone) and it means "field". However, the word หนา is a high class syllable, despite it containing a low class consonant in the onset. The syllable is pronounced "nǎ:" (with a long vowel and a rising tone) and it means "thick".
Lao.
Like Thai, Lao also has a letter that becomes silent if it comes before a low class consonant. The letter is "ho sung" ຫ, which would represent the sound /h/ if it were not paired with another low class consonant. However, unlike Thai, the digraphs beginning with the aforementioned letter can sometimes be written as a ligature.
Korean.
In Korean, the syllable structure is C(C)V(C), and Korean's writing system, hangul, reflects this structure. The only possible consonant strings must contain a glide and they must occur in the onset. However, sometimes a cluster of two consonants are written after the vowel in a syllable. In such situations, if the next syllable begins with a vowel sound, then the second consonant becomes the first sound of the next syllable. However, if the next syllable begins with a consonant sound, then one of the consonants in the cluster will be silent. For example, the word 얇다 (meaning "thin") is written as "yalb-da", but the word is pronounced as "yal-da" because the second syllable begins with a consonant sound. However, the word 얇아서 (also meaning "thin") is written as "yalb-a-sŏ" but it is pronounced as "yal-ba-sŏ" because the second syllable begins with a vowel sound.
Mongolian.
Interestingly, the native Mongolian script has much more orthographic depth than Mongolian Cyrillic. For example, the letter "Gh" or "γ" (ᠭ) is silent if it is between two of the same vowel letters. In that case, the silent consonant letter combines to two written vowel into one long vowel. For example, the Mongolian word "Qaγan" (ᠬᠠᠭᠠᠨ) should be pronounced "Qaan" (ᠬᠠᠠᠨ). In Mongolian Cyrillic, however, it is spelled "хаан" ("haan"), closer to the actual pronunciation of the word. Words in the Mongolian script can also have silent vowels as well. For Mongolian name of the city Hohhot, it is spelled "Kökeqota" (ᠬᠥᠬᠡᠬᠣᠲᠠ) in Mongolian script, but in Cyrillic, it is spelled "Хөх хот (Höh hot)," closer towards the actual pronunciation of the word.