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