# Punctuation Rules

Some punctuation rules are really just style choices (see the Punctuation Style Rules topic), although there are some concrete grammar rules in regards to punctuation. This section includes some of those concrete rules:

Commas
  There are entire courses that provide all sorts of information about the proper usage of commas. For the purposes of our documentation, a few of the most common rules are described in this section.
  Comma After an Introductory Infinitive Phrase
    Description: An infinitive is a verb form that typically begins with the word "to". An infinitive phrase includes the infinitive, plus any modifiers and complements.

    Rule: Always use a comma after an introductory infinitive phrase, unless the infinitive phrase is the subject of the sentence. It would be extremely rare for an introductory infinitive phrase to be the subject in our documentation, so you can ignore the second part of the rule. Also, when an infinitive phrase concludes a clause (rather than introducing it), no punctuation is necessary.

    Example of an introductory infinitive phrase: To add index terms to a map, open the map in the editor and add the elements.

    Example of an infinitive phrase that concludes a clause: This section explains how to create and work with projects.

  Commas (or Parentheses) Before and After Parenthetical Expressions
    Description: A parenthetical expression is a phrase or clause that is inserted within another phrase or clause.

    Rule: Use commas or parentheses (brackets) to separate parenthetical expressions.

    Example with commas: This is useful if, for instance, you want to upgrade your existing license.

    Example with parentheses: This is useful if (for instance) you want to upgrade your existing license.

  Comma to Separate an Introductory Word or Phrase
    Description: An introductory phrase, or introductory word, is simply one that begins a sentence, and includesconjunctive adverbs (such as "however", "also", "therefore", etc.)

    Rule: At the beginning of a sentence, introductory words or phrases require a subsequent comma.

    Example: In the beginning, I had no idea how to use a comma.

  Comma to Separate Each Segment in a Series
    Description: In all forms of writing, commas usually separate more than two segments in a series, although the comma before the last segment, called a Serial Comma, is considered optional and therefore becomes a style choice.

    Rule: When there are more than two segments in a series, each segment should be separated by a comma. For the purposes of the User Guide, the style rule is that we always include the serial comma when there is more than two segments (to avoid any possible ambiguity).

    Example: It provides support to help you edit, transform, and debug XML-based documents.
    Note: Do not separate TWO segments with a comma unless they are independent clauses. No comma is needed when a conjunction joins two phrases that modify the same verb.
  Comma to Separate Independent Clauses
    Description: An independent clause is a sentence that can stand on its own.

    Rule: You should use commas to separate independent clauses that are joined by coordinating conjunctions . Here is how to test it: Would the second part of the sentence (following the coordinating conjunction) make a full sentence on its own? If so, add a comma. If not, leave it out.

    Example: This tool is very powerful, and it includes a lot of user-friendly features.

  Comma to Separate Non-restrictive Clauses
    Description: Similar to parenthetical expressions, a non-restrictive clause adds extra information that is not essential to the basic meaning of the sentence.

    Rule: Use commas to separate non-restrictive clauses. When a non-restrictive clause appears in the middle of a sentence, place commas before and after it. When a non-restrictive clause appears at the end of a sentence, place a comma before it.

    Example: You can use the visual WebHelp Skin Builder tool, which does not require knowledge of CSS language, to change the overall appearance of the output.