In English, the hard c is the sound of the "c" in "cat" and "cut" (/k/) distinct from the soft c in "cent" and "city" (/s/). The soft c occurs when the "c" comes before the letters "e", "i" and "y" (as well as "ae" and "oe" in British English) and the hard c occurs elsewhere.
There are very few exceptions to this rule:
A silent e sometimes occurs at the end of a word — or at the end of a component root word that is part of a larger word — with c immediately before the silent e. In this situation, the e usually serves a marking function that helps to indicate that the c immediately before it is soft. Examples include dance and enhancement. (Such a silent e may further serve a marking function of helping to indicate that a vowel which appears immediately before that c is pronounced as a long vowel, as in rice, mace, and pacesetter.)
When adding the -ed, -ing, -er, -est, -ism, -ist, -edness, -ingness, or -(l)y–related (including -ily, -iness, -edly, -ingly, -ier, and -iest) suffixes to root words ending in "ce" in where the c has a soft-c sound and the e is silent, the following general spelling and pronunciation rule applies: the final e of the root word is dropped (except when adding the -ly suffix), and the root word (what remains of it) retains its original pronunciation, including the retention of the soft-c sound at the end of the root word.
For example, the root words dance, nice, race, self-efface, and two-face can become, with the aforementioned suffixes added, words such as danced/dancing/dancer/dancingly, nicest/nicely, racism/racist/racy/racily/raciness/racier/raciest, self-effacingness, and two-facedly/two-facedness (these last two can be pronounced "TOO-fay-sid-lee"/"TOO-FAY-sid-lee"/"TOO-fayst-lee"/"TOO-FAYST-lee" and "TOO-fay-sid-niss"/"TOO-FAY-sid-niss"/"TOO-fayst-niss"/"TOO-FAYST-niss", respectively). (The words spacey and pricey are spelling exceptions to the aforementioned rule, although they are also spelled spacy and pricy, respectively; both pairs of spellings have the expected pronunciations of "SPACE-ee" and "PRICE-ee".) The soft-c retention for all these just-illustrated suffixed words is in alignment with the general rule of pronunciation of a soft c before e, i, or y.
Adding "s" to the end of the aforementioned types of root words (e.g., wince → winces) to create a plural or third-person-singular form follows this general rule: no letters are dropped and the root word retains its original pronunciation, but the "es" at the end of the word is pronounced /əz/ (e.g., "wince" /wɪns/ → "winces" /ˈwɪnsəz/).
Essentially stated, when you add a suffix which starts with e, i, or y to the aforementioned types of root words, you generally get (that is, with rare exception) the aforementioned suffixation patterns. For adding specific suffixes (to such root words) which start with e, i, or y which weren't just mentioned (such as "-ify" and "-ize"/"-ize") — as might occasionally be added to root forms in order to create rarely-used words or neologisms — check with a dictionary, style guide, or other reliable source(s) for information and clues as to the proper suffixation form. Also, a suffix which doesn't begin with e, i, or y, if added to words which end in ce (in where the c is soft and the e is silent — e.g., "nice" + "-ness" → "niceness"; "enhance" + "-ment" → "enhancement") would typically entail no dropping of letters. Much more on the suffixation of neologisms follows later.
There are several cases in English in where two or more words are derived from the same root component(s), but one or more of them has a hard-c sound at or towards the end of the word, as opposed to one or more other words (of those being contrasted) having a soft-c sound for the analogous c in the other word(s). For example, contrast critic and critical (both with a non-initial hard c) vs. criticism (has a non-initial soft c); –and– electric (has a final hard c) vs. electricity (with a non-initial soft c). Electrician has a modified soft-c sound of "sh" as in "ship" (/ʃ/) for its non-initial c (the i following that c essentially acts as a silent, marker-letter vowel due to elision). (A similar modified-c phenomenon is also found in derived words such as logician and magician.) In all these cases, c is soft before i, but hard when before "a" or as a final letter, which mimics a general pattern found for English words.
The two-letter combination or digraph "ch" is pronounced /ʧ/| (chicken) or sometimes /ʃ/| (chef) or /k/| (choir). It can even carry, among some English speakers, the voiceless velar fricative sound /x/ in a few foreign loanwords such as Bach, loch, and chutzpah (although a majority of English speakers pronounce the ch in these words as /k/). Sometimes the /ʧ/ sound is represented by the trigraph "tch", found in non-initial positions in some English words such as clutch and pitcher. Relatedly, the "sch" letter combination is found in some English words: while it sometimes is pronounced as /sk/ as in school, it also represents an "sh" [that is, /ʃ/] sound in a few loanwords of German or Yiddish origin such as schmaltz. (Furthermore, in a few foreign loanwords, /ʧ/ is represented by "cz" [as in Czech], or "tsch" [as in Deutschmark] — and the English word fuchsia, derived from New Latin, contains a "chs(i)" combination pronounced as /ʃ/; the word is pronounced "FEW–sh'uh" [/ˈfjuːʃə/] or alternatively as "FEW-shee-uh" [/ˈfjuˌʃiə/].)
For several English verbs ending in hard c to which the past-tense -ed or present-participle -ing suffix is added, a "k" is added before the suffix to indicate that the hard c sound is preserved. This "ck" letter combination forms an endocentric digraph. Examples include panicked/panicking and frolicked/frolicking. (Arced/arcing is a notable example in where a k is not added along with these suffixes, but the hard c sound is nevertheless preserved.) The words biscuit and circuit (and derivatives such as circuitry) incorporate a silent "u" immediately between c and i, which helps to indicate that these c's (found before the silent u) remain hard in these words.
The letter combination ck is also found in many other English words, where it is also specifically found — as with the just-mentioned examples — in a non-initial position within such words. Examples include root words such as block, track, and pick (as well in as derivatives such as blocker and picking), and a number of English compound words such as jackhammer and backhoe. In all these words, it represents a single, non-elongated phonetic instance of the /k/ sound, as opposed to a doubled or geminated (i.e., elongated) /k/ being uttered (e.g., "pick" = /pɪk/ — as opposed to, for example, /pɪkːk/ or /pɪkː/ — although a semi-exception of sorts typically occurs when a ck-ending word is uttered right before another word which starts with a /k/ sound: for example, "black cat" is apt to be pronounced, due to gemination, as /blæ'kːæt/). (This gemination phenomenon [in a phonetic sense] can also occur, on infrequent occasion, within a single word when one syllable that has primary stress is next to another syllable which has secondary stress: see the "PACCORP[S]" example in the next subsection.)
A doubled c (that is, "cc") is also found a number of times in English. Except for rare examples (recce, soccer), cc is pronounced eseentially in alignment with standard rules: as /ks/ (that is, a hard c plus a soft c) in words such as succeed and success, and is pronounced as /k/ in words such as succumb and accommodate. (In the last two examples, cc also forms an endocentric digraph.)
These four prior examples (succeed, success, succumb, accommodate) follow general rules for how hard vs. soft c is pronounced based upon adjacent letters, but with the somewhat notable result that words such as succumb and accommodate just yield one "standard-length" /k/ sound as opposed to an obvious "double- or elongated-/k/" sound. (The only times we may encounter cc producing a geminated [i.e., elongated] /k/ sound is in some infrequent examples — such as combination acronyms/initialisms such as "PACCORP" or "PACCORPS" — which would likely be pronounced as /ˈpæːˌkːoʊɹ/ or /ˈpæːˌkːɔː/ or something similar.) Italian loanwords in English which contain cc can yield yet even different pronunciations for this two-letter combination (explained further on).
Furthermore, the "sc" letter combination is encountered in a number of English words: when it occurs before e, i, or y, it is usually pronounced as /s/, such as in scene, science, and scythe. In some cases, the "sci" letter combination takes on, as its sole sound or sole consonantal sound, an "sh" (/ʃ/) sound (more on this later). In other instances, sc (as well as sch, as mentioned) has a /sk/ sound, as in ascot and school; and also as mentioned, sch can carry the occasional /ʃ/ sound found in schmaltz, etc.
The "reverse" of the aforementioned letter combination — namely, "cs" — is also occasionally found, and follows a rule-based, predictable pronunciation of /ks/ in words such as ecstasy, blocs, and sacs Relatedly, the "xc" letter combination is also occasionally encountered, and likewise is fairly rule-based and predictable in its pronunciation: as /ks/ before e, i, and y (as in excess, excise, and excycle), and as /ksk/ in other instances (as in excommunicate, Excalibur, excrete, and excuse). (The "xch" letter combination, where encountered, is typically pronounced /ksʧ/, as in exchange and exchequer.)
Atypically but still relatedly, the "ces" combination is occasionally encountered as part of a "cester" letter cluster in some English/Anglosphere place names and other proper nouns, such as Worcester(shire), Gloucester(shire), and Leicester(shire). In these words, cester is pronounced /stə/ or /stɚ/, depending on local dialect. Some of the letters preceding the cester in these words can frequently be viewed as silent letters which may (or may not) be considered part of the letter combination yielding /stə/ or /stɚ/ (e.g., "Worcester" = /ˈwʊstə/ or /ˈwʊstɚ/; "Leicester" = /ˈlɛstə/ or /ˈlɛstɚ/). Essentially, we get a soft c in these words, but the c's representing it (in these words) are "phonetically packed in" with several other letters — including with an s which arguably does "double duty" with the c in rendering an /s/ sound in these words. The aforementioned words are a good example of letter sounds historically lost due to elision; the "cester" in these words is derived from Old English ceaster, which means a Roman station or walled town.
The "cqu" combination is found in a few English words such as acquittal and acquaint In such words, this letter combination is typically the same, phonetically, as how "qu" (without a c before it) is most commonly pronounced in English (that is, as /kw/).
Finally, revisiting the cz combination, it is not only found pronounced as /ʧ/| in some Slavic loanwords and Slavic names found in the Anglosphere (such as, again, Czech, as well as in many Polish surnames ending in -wicz), but the word eczema (derived from New Latin and ultimately derived from Greek) has a "more-normal-yet-modestly-atypical" pronunciation of cz among many speakers. The word can be pronounced as "igg-ZEEM-uh" /ˌɪgˈzimə/ or "EGG-zim-uh" /ˈɛgzɪmə/ or "ECK-sim-uh" /ˈɛksɪmə/ (the "/-ɪmə/" in the last two examples can also be pronounced as "/-əmə/"). Its derivative word eczematous is pronounced "igg-ZEM-uh-tuss" /ˌɪgˈzɛmətəs/ or "ick-SEM-uh-tuss" /ˌɪkˈsɛmətəs/ (the "/-sɛm-/" in these words can also be pronounced as "/-sɪm-/"). In the pronunciation versions which have a /gz/ instead of a /ks/ in them, essentially a modified hard c is being pronounced; it should also be noted that the /g/ sound is a vocalized version of the /k/ sound normally represented by hard c. The /gz/ and/ks/ pronunciation variants arise in eczema/eczematous due to anticipatory assimilation.
It is relevant to note that for many English words such as ocean, coercion, and words ending in -cious (such as delicious), the sound of c before e or i takes on a "sh" (/ʃ/) sound, which, again, can be thought of as a modified form of soft c. The first vowel after this "sh"-sounding c frequently essentially functions as a silent, marker-letter vowel which, due to elision, essentially serves to make that c "modified soft". Relatedly, in a few words which contain sci, such as conscience, omniscient, and prescient, the sc letter combination also takes on (or may take on, depending on pronunciation preferences, in the case of prescient) the "sh" (/ʃ/) sound. (The "i" in such sci-containing words also frequently essentially acts as a silent, marker-letter vowel.)
In many Italian loanwords such as cello and ciao, c before e or i takes on the Italian soft-c sound of /ʧ/ (that is, the "ch" sound in the English word "chip"), mimicking the Italian pronunciation rules for such words. (The i in ciao acts as a silent, marker-letter vowel.) A modest pronunciation exception to this latter phenomenon is found in Italian loanwords in English which contain a "sce" or "sci" letter combination, such as crescendo and fascia; the "sc" letter combination in such words is spoken as an "sh" [/ʃ/] sound.
(Further still, a semi-exception of sorts to what was just stated is found in Italian loanwords in English which contain a "cce" or "cci" letter combination, such as bocce and cappuccino; the "cc" letter combination is pronounced "ch as in chip" [/ʧ/] in these words as opposed to "k + ch as in chip" [/kʧ/] — in other words, the first c essentially behaves as a silent letter, and the second c lends a /ʧ/ sound — or the doubled c could be simply viewed as an endocentric digraph which is pronounced as the /ʧ/ sound. These various Italian-loanword exceptions [sce/sci and cce/cci letter clusters] also follow Italian rules for the pronunciation of c based upon specific adjacent letters, with the exception that double consonants in Italian [such as cc] consistently take noticeably longer to pronounce than single consonants in Italian do.)
Rarely, one may encounter instances in which one (or someone else) wants to create a suffixed form from a root word which ends in c or ce, with the suffixed form being a neologism or fanciful spelling (although the root word may or may not be a neologism or fanciful spelling itself). For example, the words sacs and blocs are both standard words (as just alluded to), merely being the plural forms of sac and bloc. However, what if we want to create the derivative forms "saciness" and "blocism"? Should they perhaps be spelled sackiness/blockism or sac-iness/bloc-ism or some other way? On a similar note, let's say that we have three aspiring artists, all making a minor buzz in artistic blogger circles, and all with unique artistic styles: they are named Trac (pronounced "trace" /treɪs/; the name is short for Tracy), Dac (rhymes with "trace" /deɪs/; the name is short for Dacian), and Cece (pronounced "SEE-see" /ˈsisi/). Would artistic styles and adherents of such styles be referred to, for our first artist, as Tracism/Tracist or Traceism/Traceist or Trac-ism/Trac-ist or something else?
Unfortunately, no standard conventions exist with such word formations, but hints derived from any past written forms we may find, including from the way certain standard words are constructed, can help us here. Avoiding excessive confusion and ambiguity are also important. Arguably, for the aforementioned derivatives we want to form from sac and bloc, the forms "sac-iness" and "bloc-ism" would be best, absent any strong clues or directives to write them otherwise — a key reason for this still-debatable decision is to avoid ambiguity and confusion with the words "sack" and "block", which are also standard English words which are used more than sac and bloc.
Arguably another trait going for this decision is that there are almost no examples, save for some protologisms, of short, c-ending words similar to “sac” and “bloc” found elsewhere in English which add a k before an added suffix. (Talcked/talcking, which can also be spelled talced/talcing, is such a very rare exception; however, the words syncing/synced [also alternatively spelled synching/synched and pronounced the same]; the slang derivatives narcing/narced [from “narc”, meaning “to rat out and betray”, although also occasionally spelled narcked/narcking or narked/narking]; and the occasionally-found colloquial derivatives calcing/calced [short for calculating/calculated], are additional, non-neologism derived (inflected) forms whose root ends in c — but which typically or frequently don’t add a k when inflected as such. (Note: Calced is also a standard English word which is used to refer to religious orders which wear shoes, as opposed to those orders which do not wear shoes as a sign of austerity; in this particular definition case, the word is pronounced /kælst/ — notably, with a soft c [sound] in the middle of the word.) However, in regards to the “sac-iness” example just focused on, another thing we could do, in place of writing “sac-iness”, is to write "saclike nature" or something similar with “saclike” in it, since “saclike” is an established word.
For our three aspiring artists, the forms Tracism/Tracist, Dacism/Dacist, and Ceceism/Ceceist are all arguably decent choices: this is due to the "clean and normalized" situation we have with the first two artists' suffixed derivatives: namely, the "i" acting as a marker vowel to help indicate a soft c pronunciation, and also helping to indicate that the a is pronounced as a long vowel. And, the long e that appears as the fourth letter in Ceceism/Ceceist, when the "-ism" and "-ist" suffixes are added, does not conflict with the rule to drop an e which is silent that we would incur when turning the word dance into, say, dancing or dancily. However, until the artist Trac becomes rather well-known and established (at least within artistic circles), it may be easier to the reader to use Trac-ism/Trac-ist in order to avoid ambiguity and confusion with the word "trace".
If adding suffixes, especially -ed and -ing, to one of the three artists' names (if we were "verb-ing" them), we could even use an apostrophe instead of a hyphen (i.e., Dac'ed, Cece'ing), depending on stylistic tastes and clues of past usage. Such apostrophe usage arguably may be even a bit more acceptable to do if applied to root words of similar nature which are short, and arguably may be even a bit further acceptable to do if the root word is both short and entirely in lowercase form (e.g., dac'ed, cece'ed, cece'ing; also: cece'd may be an acceptable alternative to cece'ed due to the e at the end of the root component — especially given the non-silent e that it is [in this very latter example]).
And again, past patterns found in established words can be a good guide of what to do. If the words "prolic" (rhyming with "frolic") and "quentric" (rhyming with "centric") suddenly came on board, at least as neologisms, the "k-added" forms prolicked/prolicking and quentricked/quentricking would likely be readable and reasonable choices for most reading audiences. This is due to the similar pattern found in words such as frolicked/frolicking and panicked/panicking. Yet again, one can use hyphenated suffixes (e.g., "quentric-ed") if one is not sure what to do, unless an established style guide (or strong, reasoned gut feeling) being followed disallows this.
One more thing to examine is whether it is acceptable to drop letters as opposed to adding any letters (such as adding a k to a suffix as just mentioned). What if, for example, Dac's name were spelled "Dace" and still rhymed with "trace"? If we wanted to "verb-ize" the name in a present participle form, would "Dacing" be okay? It may well be, as it follows normal patterns of dropping a silent e, and the "ing" letter cluster acts as a set of marker letters to give the idea that the a is still pronounced "long". If we had a lowercase d (that is, "dace"), perhaps a hyphenated/"apostrophed" form (i.e., dac-ing, dac'ing) would be better, to avoid confusion with the word "dancing". Again, as just alluded to, also judge how new the suffixed word is, and any clues regarding past usage, in helping to decide what to do.
But, if the name were spelled "Dacc" and still pronounced the same, we probably don't want to drop letters due to the lack of an established pattern in English to do so (if making a derived form out of Dacc, such as "Dacc-ing") — and it may well be best to use a hyphen or at least an apostrophe (at least in the protologism stage with this word) to indicate that no c is pronounced hard, and that the a is not long. But further, if the spelling were "Dacce" (still pronounced the same, but with a silent e), it may be okay to drop the e if making the neologism "Daccing", but we may still want to not do this (e.g., "Dacceing") or use a hyphen/apostrophe also with no letters dropped (e.g., "Dacce-ing") if the word is very much a protologism.
The key issue is: Pay attention to what the reader is likely to interpret. Some very final examples: Dac's name instead rhymes with "make" (IPA: /deɪk/; that is, with a hard c instead), or still kept the soft c but instead rhymes with "lass" or "boss" (IPA: /dæs/ or /dɔs/). In these examples (assume we're still making suffixed protologisms here), the use of a punctuation-separation device (e.g., Dac-ed, Dac'ing) may well be best with these suffixations, in order to help indicate not to pronounce a soft c with the /deɪk/ example, and not to pronounce a "long a" with the other two examples. If Dac's name were pronounced like "dack" or "dawk" (IPA: /dæk/ or /dɔk/), the use of a hyphen before the added suffix (e.g., Dac-ed, Dac-ing) may well be best (i.e., the hyphen attempting to better cue the reader: "no soft c/no long a"), with the arguable exception of Dac'd as a past-tense form. Again, taking reasonable steps to avoid ambiguity and confusion will significantly help the reader — and, again, the writer should look for clues regarding past usage if such clues do or might exist.
Due to the hard/soft dichotomy of c in English, as well as how vowels next to c can perform specific marking functions (e.g., indicating that the c is hard or soft, or that an adjacent vowel is long or short, etc.), writers sometimes use special symbolic accompaniments with c (or with adjacent letters) to ostensibly avoid ambiguity for the reader. (This scheme was previously alluded to in the "Suffixation of Neologisms" section above.) Creative examples using this scheme include Lōc-ed After Dark, a 1989 chart-topping album from American hip hop musician and actor Tone Lōc; and Marxist philosopher Andy Blunden's use of the protologism "farçade" (with an "r" in there) in response to an idea within a treatise written by prominent British sociologist Anthony Giddens.
In the former example, the hyphenation helps to convey that the c is to remain hard by "keeping it away from" an e, and the macron (i.e., line) over the o conveys that the o remains long despite the hyphenation. (The hyphen, despite its usefulness in "keeping the c hard", largely "takes away" the "marking ability" of the right-after-the-hyphen silent e that otherwise would help it indicate that the o is pronounced long. Thus, adding the macron over the o fairly clearly indicates to "pronounce this o as a long vowel".) In the latter example, "farçade" is ostensibly a portmanteau of the words farce and façade The cedilla below the c in farçade helps indicate to pronounce the c as soft (similar to how "ç" is pronounced in French), and also helps to draw an analogy to the standard-English word "façade" (and thus, to further cue the reader to pronounce the "a" after the "ç" in the protologism farçade as "ah" rather than as "ay"). (Façade [without an r] is frequently written in English without the cedilla; as such, including the cedilla in the protologism farçade helps strengthen the pronunciation analogy between farçade and facade/façade.)
More often, within English-language media, alternative-spelling schemes involving the replacement or substitution of a c (and/or, on occasion, special symbolic-type markings added to c, such as a vertical line through c to make the cent sign [e.g., "common ¢ents" as a wordplay on "common sense", appearing in some pamphlet on personal finance]) are encountered not as a pronunciation aid, but essentially as a way to convey a special meaning or mood and/or add to the catchiness of a word or name. Diacritical markings added to letters adjacent/close to c in c-containing words/names, as occasionally encountered elsewhere (such as with Cēpacol, an American product-brand family for health and personal-hygiene products; and with the diaeresis-containing coöperate, an alternative spelling of cooperate), typically are meant to help with pronunciation, however. And, as previously illustrated, the use of added punctuation (such as a hyphen immediately following a c) in an "attempts-to-avoid-having-a-confusing-c" word/name — such as in, say, the portmanteau designator "PAC-EAST" being used as a fully-capitalized short form for the CamelCase spelling "PacificEastern" — can help the reader with pronunciation as well as overall meaning.
(It should be mentioned that there are a few words in English which only appear in certain English-language dictionaries [such as the Oxford English Dictionary’s unabridged, concise, and shorter versions, as well as the Merriam-Webster OnLine dictionary] with a cedilla-containing c, such as with the French-derived words garçon and soupçon [In other words, the spellings “garcon” and “soupcon” [without cedillas on/under the c’s] do not even appear as secondary or alternative spellings in these just-mentioned dictionaries.])
Below are several further examples, involving atypical/fanciful spellings, and further involving the replacement, substitution, or modification of a hard or soft c (or the replacement/substitution/modification of something related to them):
In Italian and Romanian, the phoneme /k/ can occur before "e", "i" and "y" by putting an "h" after it (Italian chiaro, /kjaro/, clear). Conversely, in Italian and Romanian, c is made soft by adding an e or i after it (Romanian ceas, /ʧas/, hour; Italian ciao, /ʧao/, goodbye). In French, Catalan, and Portuguese, the phoneme /s/ is produced before "a" or "o" or at the end of the word by adding a cedilla (French garçon, /gaʀsõ/, boy; Portuguese coração, /koɾasɐ̃u/, heart).