Semicolons (;) act as both periods and commas. They work as periods because they are used after a complete thought; they work as commas because they show that the two complete thoughts are related.
If you have: In order to separate two complete thoughts in the same sentence, insert a comma followed by a conjunction (for, and, nor, but, or, yet, so).
For example: The mirror shattered, and the pieces went everywhere.
Replace it with: Use a semicolon to separate the complete thoughts.
For example: The mirror shattered; the pieces went everywhere. The semicolon shows that the two sentences are related, and it provides variation in sentence structure/length.
Parentheses ( ) separate nonessential information (information that the author wishes to add but that does not necessarily need to be included). from the rest of the sentence.
If you have: Commas separate unnecessary information from the rest of the sentence.
For example: In The Princess and the Frog, Tiana makes the best beignets, delicious Louisianan pastries.
Replace it with: Parentheses separate extra information from the primary text.
For example: In The Princess and the Frog, Tiana makes the best beignets (delicious Louisianan pastries). The parentheses show that the phrase “delicious Louisianan pastries” is helpful to the reader but not necessarily essential to understanding the sentence.
Colons (:) are used for reiteration or description. The information after colons refers to the information that precedes them: it denotes a question and answer.
If you have: Commas separate items in a list.
For example: We had a Lord of the Rings marathon last night because we watched The Fellowship of the Ring, The Two Towers, and The Return of the King.
Replace it with: Use a colon to show that the second part of the sentence reflects/answers the first.
For example: We had a Lord of the Rings marathon last night: we watched The Fellowship of the Ring, The Two Towers, and The Return of the King. Using a colon here makes the sentence more exciting. It provides the answer to the question of what classifies as a Lord of the Rings marathon.
Em Dashes (―) separate specific information from the rest of the sentence. They—by disrupting the sentence—suggest changes in tone or meaning.
If you have: Commas set off extra information in sentences.
For example: My dog, “man’s best friend,” left me at the park.
Replace it with: Replace the commas with em dashes and separate the extra information from the sentence.
For example: My dog―“man’s best friend”―left me at the park. In this sentence, the em dashes set off the sarcastic phrase, giving more of a distinct tone to the sentence.