Colon 
)
* Punctuation used to introduce explanatory information such as tabulations, lists, etc.; for salutations, as 'Dear so-and-so'; in clock time (e.g. 2:15); for periodical reference (e.g. 4:3); and between book title and book subtitle (e.g. Dictionaries: The Art and Craft of Lexicography).
* A colon is used before a final clause that explains or amplifies something in that sentence, e.g. The dissertation needs work: it lacks flow.
* A colon introduces a series or summarizing statement, e.g. The following is on our list of places to go: grocery store, toy store, doughnut shop., She had one great love: him.
* A colon is used in proportions, e.g. 2:1, and as a ratio sign, e.g. 1:2::3:6.
* A colon may introduce a quotation, especially a long one. Colons go outside quotation marks unless they are part of the quotation itself. A colon also is used to end all paragraphs that introduce a paragraph of quoted material.
* A colon is used in dialogue text, e.g. Kyle: Do you want to have lunch? Holly: Yes.
* A colon is used in correspondence for headings and introductory terms, e.g. To:, From:, Re: and to separate writer/typist and carbon-copy abbreviations from the recipients.
* A colon can give emphasis, e.g. He had only one hobby: eating.
* Capitalize the first word after a colon only if it is a proper noun or starts a complete sentence, e.g. Scientists have found a name for the opposite of gravity: levity. The panel consists of: Dr. Juli, Dr. Kipfer, and Dr. Bellantoni.
* Do not combine a dash and a colon.
Comma ( ,)
Punctuation most commonly used to separate or set off items as:
* Separate items that might otherwise be misunderstood, e.g. What the problem is, is not clear.
* Separate members of a series used with 'and', 'or', or 'nor', e.g. The flag is red, white, and blue.
* Separate main clauses or before the conjunction in a compound sentence, e.g. Either you start doing more work, or you will have to look for a new job. She was glad she had looked before backing out, for a child just whizzed by on the sidewalk.
* Separate two verb phrases in a sentence, e.g. She did earn a Master's, but now she is going to go on and earn a Ph.D.
* Set off subordinate clauses/phrases within sentence, e.g. On the street, the partygoers gathered for the fireworks.
* Set off an apposite (noun referring to previous noun, e.g. my sister, Nancy) or contrasting words/phrases (e.g. I need you, not anyone else.).
* Set off introductory items, clauses, or phrases, e.g. "Sir, are you listening?".
* Set off interrupting or parenthetic items, e.g. He has no reason, does he, to want to play basketball for that coach?
* Before a quotation following an introductory phrase, e.g. "She said quietly, "I love you." Inside a closing quotation mark, e.g. I said "wash," not "drawer." Commas always go inside quotation marks in American English usage.
* To show omission of a verb or predicate, e.g. Brad Pitt once worked as a giant chicken; Rod Stewart, as a gravedigger; Whoopi Goldberg, as a makeup artist in a mortuary.
* Between compound qualifiers / equal adjectives, e.g. He has big, broad shoulders.
* Between name and title, title and organization, name and degree, surname and Junior/Jr./Senior/Sr. In an inverted name, e.g. Kipfer, Barbara Ann.
* To separate thousands, millions, etc. in numbers of four or more digits, e.g. 2,000.
* To set off the day of the month, e.g. They got together on June 1, 1991, for the first time. To set off elements of an address, e.g. Write to him at The Language Centre, University of Exeter, Exeter, England EX4 4QH.
* After the salutation in informal correspondence, e.g. Dear T.B., and after the complimentary close in all correspondence, e.g. Respectfully,.
* To separate states and nations used with city names, e.g. LaPorte, Indiana.
* To set off yes and no, e.g. No, I will not be there
Semicolon (; )
Punctuation sometimes regarded as a weak period or strong comma and used in ways similar to periods and commas. A semicolon can mark the end of a clause and indicate that a clause following is closely related to the previous clause. A semicolon can also divide a sentence to make meaning clearer. A semicolon is placed outside quotation marks and parentheses. Uses are:
* Separates (but also links) independent clauses in place of a coordinating conjunction or ellipsis, e.g. The package was due last week; it arrived today.
* Separates (and links) independent clauses when the second clause begins with a conjunctive adverb such as: accordingly, all the same, also, as a result, besides, by the same token, consequently, furthermore, hence, however, indeed, in that case, likewise, moreover, nevertheless, on the other hand, otherwise, still, then, therefore, and thus. These usually explain or summarize preceding matter or show some kind of transition, e.g. We organized enough work for the rest of the summer; therefore, I can plod ahead.
* Clarifies meaning in long sentences and in those with several commas. The indication of a strong pause by the semicolon helps the reader understand the meaning.
* May be used before explanation phrases and clauses as: e.g., for example, for instance, i.e., namely, that is - e.g. She is highly qualified for the job; for example, she has worked for more than twenty years as a writer and editor.
* Separates lists or phrases in a series when the phrases themselves have commas, e.g. We visited Springfield, Massachusetts; Keene, New Hampshire; and Durham, New Hampshire.
