In contractions, an apostrophe normally replaces omitted letters. Examples: don’t, can’t, won’t, shouldn’t, wouldn’t. Other examples are: singin’, ’tis, and rock ‘n’ roll. Some contractions, such as won’t or ain’t, are formed irregularly. Colloquialisms such as gonna and wanna take no apostrophe since there is no place for one.

To avoid confusion, lowercase letters form the plural with an apostrophe and an “s.” Example: x’s and y’s.

In informal writing the first two digits of a particular year are often replaced by an apostrophe. Example: the class of ’62.

Whenever you are using an apostrophe, be sure to use the symbol for an apostrophe and not use the symbol for a single quotation mark. They are different: ( “ ‘ ” vs. “ ’ ”).

This concludes the four-part series on apostrophes.

In compound nouns and noun phrases the final element usually takes the possessive form. If plural compounds pose a problem, use “of.” Examples: a cookbook’s recipes my daughter-in-law’s profession, but the professions of both my daughters-in-law.

In proper names or where there is no clear possessive meaning, the apostrophe is omitted. Examples: Publishers Weekly, CLASS Christian Writers Conference, Department of Veterans Affairs, a housewares sale.

When neither an “s” nor an apostrophe alone look right, avoid the possessive and use
“of” instead. Example: For the love of Jesus.

Possessives, such as hers, yours, and its, have no apostrophe. Example: The dog scratched its fleas. “It’s” is the contraction for it is. Example: It’s going to rain today.

Exceptions to the rule of adding an apostrophe “s” for the possessive form are the possessives of ancient proper names ending in “s.” Examples: Moses’ Law, Jesus’ parables, Euripides’ tragedies, Xerxes’ armies.

To avoid an awkward appearance, an apostrophe without an “s” may also be used for the possessive of singular words and names ending in an unpronounced “s.” Examples:
Albert Camus’ novels, Descartes’ three dreams, Vaucouleurs’ assistance to Joan of Arc.

For … sake expressions traditionally omit the “s” when the noun ends in an “s” or “s” sound. Examples: for righteousness’ sake, for goodness’ sake, for Jesus’ sake.

Closely linked nouns are considered a single unit in forming the possessive when the entity possessed is the same for both. Only the second element takes the possessive form. Example: my aunt and uncle’s house. When the entities are different, both nouns take the possessive form. Example: my friends’ and neighbors’ children.

The possessive of most singular nouns is formed by adding an apostrophe and an “s.” The possessive of plural nouns (except for a few irregular plurals that do not end in “s”) is formed by adding an apostrophe only. Examples: the horse’s mouth, a bass’s stripes, puppies’ paws, children’s literature.

This general rule covers most proper nouns, including names ending in “s,” “x,” or “z,” and both are singular and plural forms, as well as letters and numbers. Examples: Chicago’s lakefront, Massachusetts’s legislature, Burns’s poems, Marx’s theories, Berlioz’s works, the Lincolns’ marriage, FDR’s legacy, 2003’s heaviest storm.

When the singular form of the noun ending in “s” looks like the plural, and the plural form is the same as the singular, the possessive of both singular and plural is formed by adding only an apostrophe. Examples: politics’ true meaning, economics’ forerunners, this species’ earliest record.

The same rule applies when the name of a place or an organization is the plural form ending in “s,” such as the United States, even though the entity is singular. Examples: the United States’ role in world peace, Marvin Gardens’ former curator, Greenwood Hills’ last mayor.

The em dash, often just called the dash, is the most commonly used of the dashes. To avoid confusion, no sentence should contain more than two dashes. A pair of em dashes sets off an amplifying or explanatory element. Commas, parentheses, or a colon may perform a similar function, but em dashes are often used for emphasis. Be careful not to overuse them though.
Example: the influence of three Impressionist artists—Monet, Sisley, and Degas—is obvious in her beautiful portraits.

An em dash may be used to separate a subject, or a series of subjects, from a pronoun that introduces the main clause. Example: Broken promises, petty rivalries and false rumors—such were the obstacles they kept her from advancing in the company.

An em dash, or a pair of em dashes, can indicate a sudden break in thought or an interruption in dialogue.
Examples: Will he—can he—win the race?
“I don’t know what to say,” I began softly, “I thought I might—“

Hyphens and dashes all have specific uses. They cannot be used interchangeably.

The hyphen is used to separate compound words, either a compound noun or a compound adjective modifying a noun. If there is more than one phrasal adjective modifying a single noun, hyphenation becomes especially important.
Examples: fuzzy-wuzzy bear, video-game-magazine dispute, state-inspected assistant-living facility, twenty-four hours, twenty-four-hour clock.

The hyphen is also used to separate numbers that are not inclusive, such as telephone numbers, Social Security numbers and ISBN numbers.
Example: Her telephone number is 501-324-7611.

Another use for the hyphen is to separate letters when the word is spelled out.
Example: Her name is Alayna, spelled a-l-a-y-n-a.

In URLs careful distinction needs to be made between a hyphen (-), a tilde (~), and an underline (_). Examples: http://www.rz.uni-karlsruhe.de/~szm http://www.ucsb.edu/univ_press/ . If you want people to easily find your website or your e-mail address, it is best not to use any of these three since they are easily confused.

The exclamation point is used to make an emphatic statement, an outcry, or an ironic comment. Again: do not double punctuate! Two exclamation points are no stronger than one, and be careful to use exclamation points sparingly.
Example: Look out!

A question that is essentially an exclamation usually ends with an exclamation point.
Example: How could you possibly do that to me!

And exclamation point should be placed inside quotation marks, parentheses, or brackets, only when it is part of the quoted or parenthetical matter.
Examples: The woman exclaimed, “That car hit the tree!”
Jenny kept repeating, “I could have died!” throughout the whole questioning.

The question mark is used to ask a direct question, to indicate an editorial doubt, and to express surprise. Never double punctuate. Don’t use two question marks together or a question mark and an exclamation point.

Examples: When will Taylor’s car be ready?
The world population is estimated to be 7.029 billion? by the United States Census Bureau.
That is your answer?

A question mark is used within a sentence at the end of the direct question. If the question does not begin the sentence, it doesn’t need to start with a capital letter.
Example: The question, how long is this meeting going to last? was on everyone’s mind.

An indirect question never takes a question mark.
Example: He wondered if it was time to go home.

When a question within a sentence consists of a single word, such as who, when, how, or why, the question mark may be omitted, and the word is sometimes italicized.
Example: The question was no longer how but when.

A request disguised as a question does not require a question mark.
Example: Will the congregation please rise.

A colon is used to introduce an item in a series of items that describe or amplify what has preceded the colon. Example: Sarah’s exercise program involves three objects: a stationary bicycle, an exercise ball, and 2-pound weights.

The colon may be used instead of the period to introduce a series of related sentences.
Example: Karen was faced with a difficult choice: Should she tell her husband what happened to the car? Or should she remain silent and get it fixed herself?

Colons are also used in URLs, but no space precedes or follows a colon in this case.
Example: An excellent place to find many versions of the Bible is http://www.BibleGateway.com/.

When a colon is used within a sentence, the word following the colon is lowercased unless it is a proper name. When a colon introduces two or more sentences, a speech in dialogue, or a Bible verse, the first word following the colon is capitalized. Example:
Philippians 3:14 states: “I press on toward the goal to win the prize for which God has called me heavenward in Christ Jesus” (NIV).

The semicolon is stronger than a comma but weaker than a period. However, it can assume either role, although its function is usually closer to that of a period. Semicolons should be used sparingly since they often cause sentences to be long and cumbersome.

The most common use of a semicolon is between two independent clauses that are not joined by a conjunction. Example: The road was long; the road was dangerous.

A semicolon should precede adverbs such as then, however, thus, hence, indeed, besides, and therefore when it is use transitionally between two independent clauses.
Example: Richard is going to London; however, he doesn’t have his reservations yet.

When a semicolon is called for at the end of material enclosed in parentheses or brackets, the semicolon should follow the closing parenthesis or bracket. Example: She placed her manuscript in an envelope (her final draft); then, with relief, she sealed the envelope.