Although many have studied it, no one has successfully explained it.
      (introductory phrase/clause separated from main clause)

      When the novel was published, //it was widely attacked by critics and the public,
      //for it took highly unusual risks and spoke openly of sex, //a subject not discussed
      openly at the time.
      (commas separate introductory clause, independent clauses, final descriptive phrase)

*    to set off parenthetical phrases that "digress" or "interrupt" the flow of a sentence:

      The novel, written forty years ago, has a timeless quality.

      It has devoted fans who, though they tend not to be academics, are nevertheless
      articulate and persuasive in its defense.

*    between adjectives before a noun:  She has a terse, compressed writing style.

*    between items in a list:  He wrote novels, plays, poetry, and film scripts.

      He was reclusive, ornery, and fabulously wealthy.
 

*    to separate independent clauses closely related to each other (an independent clause
      is part of a sentence that could stand alone as a separate sentence):

      The narrator is highly unreliable; he lies on several occasions.

      The critics were unanimous in their praise; however, the sales were terrible.

*    for clarity, to act as commas in a list in which there are already several commas:

      There were public performances on Sunday, February 2nd, 1886; Thursday, July 2nd,
      1887; and Monday, September 6th, 1888.

      The setting has everything a gothic novel needs, including an ancient, decrepit
      castle filled with friendly bats; a madwoman, who turns out to be the hero's mother,
      locked in an attic room; and nearly constant lightning storms, even in the dead of
      winter.
 

*    before an example:

      His career was marked by terrible decisions:  for example, his marriage.
 
      He is hardly unbiased toward his boss:  he calls her, at one point, a "tyrant" (344).

*    before a quotation used to exemplify a point:

      In chapter 28, she finally tells her mother what she thinks:  "                      "
      (Note:  if the quotation is long, it is indented WITHOUT quotation marks.)
 

*    A hyphen makes compound words:        ten-year-old boy        nine-year cycle

      It also separates prefixes:            self-respect            cross-cultural

*    A dash  separates words as a comma does; it is like a stronger comma or sometimes
      like a colon.  It SETS OFF words at the end or in the middle of a sentence.

      Her poetry was characterized by two features--strong images and complex tone.
 
      The major features of her poetry--strong images and complex tone--were often
      praised by critics.
 

                Singular                                                                Plural
            (before the "s")                                        (after the "s" unless the plural doesn't use "s")
      my brother's house                                                    my brothers' house(s)
      a woman's perspective                                              women's perspectives
      this society's restrictions                                            many societies' restrictions

*    to stand for letters left out in contractions:  can't, wouldn't, I'm

*    the great ITS/IT'S problem:  possessive or contraction?

      Its  is POSSESSIVE:  The college rewards its employees.

      It's  is a CONTRACTION:  It's a long time until spring.

      NOTE:  Its' doesn't exist!