Let’s talk about the dos and don’ts of contractions, ’k?
(But first, this note: This punctuation mark is the same as the one used for apostrophes. However, if you use smart, or curly, quotes, your word processing program will probably incorrectly render an apostrophe not preceded by a letter — as in the last word in the opening sentence — as an open single quotation mark, so you have to outwit the witless program by copying and pasting a closed single quotation mark or an apostrophe, or typing a character followed by the proper mark, then deleting the first character.)
In a given piece of prose, the presence or absence (or relative prevalence) of contractions, or words in which one or more letters is elided or replaced — often but not always with one or more apostrophes as markers — is one of the primary determiners of formal or informal writing.
Some publications go so far as to prohibit ubiquitous contractions such as can’t, won’t, and related terms, as well as he’s and she’s, considering them inappropriate in authoritative composition. Meanwhile, some contractions are widely thought of as unseemly except when transcribing dialect or preserving archaic forms in the proper context. Here are some classes of contractions:
Gonna, wanna, and the like are considered appropriate in formal writing only when faithfully capturing colloquial speech. The same goes for such elisions as ’em (for them) and ’cept (for except). Other nonstandard forms communicating nonstandard dialect, acceptable only in narrative or dialogue in informal contexts, include ’fraid, ’nother, s’pose, and t’other.
Venerable contractions such as ’twas are mostly seen in historical contexts, though they might be employed for humorous effect, such as to produce a faux-archaic sense. ’Tis time to get o’er it, e’en so. Others, seen usually in poetry, include ’gainst, heav’n, and wither’d and many other words in which the -ed ending is so elided to conform to poetic meter or prose rhythm. Similar constructions, like ha’e (have), i’ (in), th’ (the), and wi’ (with), are seen in the poetry of Robert Burns or other reflections of dialect.
A few words with contractions are incorrect any other way, and their elided forms must be honored even in the most formal contexts. These grandfathered elders include the o’ compounds cat-o’-nine-tails, jack-o’-lantern, o’clock, and will-o’-the-wisp. Ne’er-do-well is another phrase given a pass.
However, Halloween, formerly spelled Hallowe’en (from “Hallow evening,” referring to All Hallow’s Eve), has lost its contraction marker, and the maritime slang fo’c’s’le (pronounced FOKE-sul) is often spelled out in full (forecastle), though the latter use in most nautical dialogue would be clumsy and stiff. By the same token, boatswain is, outside technical contexts, spelled bosun or even bos’n. Cap’n, however, is an informal contraction of captain that, unlike bosun, is not generally seen outside dialogue.
Contractions with More Than One Apostrophe
He’d’ve and its feminine and plural equivalents, and wouldn’t’ve and similar words, are technically correct but inappropriate for formal writing. But in informal contexts, bring ’em on.
“Rock ’n’ roll” requires an apostrophe on each side of the letter n, to mark the preceding and following letters in and. Better yet, though, follow the spelling in most dictionary entries for the term and spell out and, just as in “rhythm and blues.”
Full words such as copter or phone, formed by omitting one or more syllables from the beginning or end of a word (or, rarely, from both, as with flu being derived from influenza), do not feature an apostrophe, but some writers included the markers when the clipped forms first appeared in print, so this form is acceptable in limited usage, such as in a historical novel.
Abbreviations of years, such as in the phrases “spirit of ’76” and “class of ’84,” require apostrophes.
’Til is acceptable in informal writing, but till is preferable, and until is more appropriate in formal contexts.
Two contractions rarely seen outside column headings in charts or in newspaper headlines, where, because of space limitations, they are usually compressed, are ass’n (association) and ass’t (assistant).
Although terms like Mr., Jr., and Ltd. elide letters (and, outside American English, the periods are omitted), they are technically abbreviations, not contractions, because apostrophes are not used.
Notes about the First Paragraph
Let’s is the only contraction I can think of that is bereft of a viable full form; nobody writes “Let us” as the beginning of an invitation unless they intend to affect a stiff formality. Also, the treatment of “dos and don’ts” is correct; don’ts includes an apostrophe only because don’t does. (Dos and don’ts are plural forms, not possessive ones.) Finally, ’k (or ’K) as a perky contraction of OK belongs only in social media contexts or as a snide parody of such usage.