Silent and invisible letters in English
Silent letters constitute a notorious phenomenon in English: in wréstle, for example, only four out of the seven letters are actually sounded (*résl), and there can be strings of them in place names, exemplified by the trio Léicester, Glóucester and Worcester, pronounced Léster, *Glóster and *Wùster. (The accents show stress and pronunciation, see English spellings; * is placed before an incorrect spelling.)
Silent letters can be misleading, as in Thaîland and îsland, which rhyme, or they can be easy to ignore, as in wróng, yeôman, and lôw. They can serve to distinguish between words that sound the same:
knôw knowledge = nô negative
knót tie = nót negative
wráp parcel = ráp knock, talk
wrîte read = rîght correct = rîte ritual
chéck verify = BrE chéque money
Typical silent letters are b finally after m or before final t (-mb -bt); g or k initially before n (gn-, kn-); gh finally or before final t ( -gh -ght); l after à and before final f or m (-lf -lm); n finally after m (-mn).
List of examples
Only J, Q and V are sounded in every word in which they occur.
Silent A is found in: hëard, lëarn, Múrray = Mòray, nébulaê; British English words ending in -ary: sécondary, díctionary; and all BrE examples from Latin of aê: nébulaê, fŏrmulaê (where American English omits the 'a')
B: thúmb, dúmb, númb, clîmb, límb, débt, dòubt, súbtle
C: indîct, Tûcsón, Connécticut, blancmànge, (*bləmónzh); after s before a front vowel: scêne, scîence, effervésce
CH: yàcht (*yót)
D before a soft g: dódge, édgy, lódging, bádger, brídge, wédge; for most speakers in Wédnesday; and before a French j in Djiboûti, Abidjàn
E: heàrt, heàrth, yeôman; final mute as in lâte, kîte, hôpe, Jûne; in regular past tense ending as in loòked, and both of these as in hoped; síngeing (*sínjing, from sínge)
F: hâlfpenny
G: sîgn, desîgn, dèign, rèign monarch (= rain weather), campâign, fóreign, phlégm, gnásh, gnåw, gnôme, gnát, gnàrled, Colôgne
GH: sîgh, rîght, fíght, fríght, night, fŏught, ŏught, cåught, èight, wèight
H: hônour, hónest, héir, hòur, vêhicle, Jóhn, Thaîland, ghôst, ghàstly, and in the BrE name-suffix -ham: Béckenham, Chéltenham, Twíckenham
I: sûit, recrûit, frûit, jûice, sluîce, brûise, crûise, pláit, friénd, pàrliament, cárriage, márriage
K, initially, before n: knôw, knêe, knîght, knít, knâve, knóll, knót, knîfe, knêad massage; after c, as in báck
L: càlm, bàlm, psàlm, càlf, càlve, hàlf, hàlve, fôlk, tålk, wålk, sálmon, Líncoln, hâlfpenny
M: mnemónic
N: cólumn, condémn, hýmn, åutumn, dámn, sólemn
NC: blancmange (*bləmónzh)
O: pêople, léopard, jéopardy, Géoffrey (= Jéffrey) and all BrE examples from Latin of oê: phoênix, oênólogy, foêtus (where AmE omits the o)
P: recêipt, pneumátic, pneumônia, psàlm, pseûd, ptàrmigan, pterodáctyl
R: all BrE only; a small selection: îron, àrm, àrt, céntre, mürder, pãir, mŏre, dŏor, desîre, squãre, hîre, përson, Thürsday
RPS: cŏrps (r sounded in AmE)
S: chássis, prècis, Àrkansås, Íllinois, îsland, îsle = aîsle, rendezvous (*róndâyvoô)
T: lísten, whístle, wréstle, càstle, mústn’t, bùffèt, óften, mŏrtgage, bìdèt, Màrgot, wåltz (*wålce), bôatswain, (can be written bôsun), Tchaikóvsky, tsunàmi, and before ch in words such as ítch, cátch
U: bìscuit, cïrcuit, buíld, buŏyant, guíld, guílt, guîde, guàrd, guéss, guést, āunt
UE: tòngue, burlésque, grotésque, vâgue, rôgue, barôque, unìque, plâgue; BrE only: cátalógue, dîalógue (-lóg in AmE)
W: two 2 (= to preposition = toô many, also), who (*hû), whôle entire (= hôle space), swŏrd, ànswer, wrîte paper, wróng, wréstle, awrŷ, åwful, bôatswain (can be written bôsun), and before a consonant in the next word: knòw, nòw, yew tree (= yoû me)
X: faux-pàs (*fô-pà) and French plurals of -au words: cháteaux (*shátô), tábleaux (táblô)
Y: Pêpys (= pêeps), Sándys (= Sánds = sánds)
Z: lâissèz-fãire, rendezvous (*róndâyvoô)