Here are the main reasons to use a semicolon:
1. To connect two closely related independent clauses without a conjunction:
* Example: The storm raged outside; the house shook violently.
2. To separate independent clauses when they are already joined by a conjunctive adverb (like "however," "therefore," "moreover," etc.):
* Example: The movie was long; however, it was very entertaining.
3. To separate items in a list when the items themselves contain commas:
* Example: We visited London, England; Paris, France; and Rome, Italy.
4. To separate long or complex sentences:
* Example: The train was delayed; the tracks were damaged; and the passengers were restless.
Important points to remember:
* A semicolon always goes before the second independent clause.
* Don't use a semicolon to separate a dependent clause from an independent clause.
* Don't use a semicolon when you can use a comma and a coordinating conjunction (like "and," "but," "or," "so," etc.).
Here are some examples of incorrect semicolon usage:
* Incorrect: The dog barked; at the mailman. (The second clause is not an independent clause.)
* Incorrect: The cat chased the mouse; and caught it. (Use a comma and conjunction instead.)
If you're ever unsure whether to use a semicolon, it's best to check a style guide or ask a writing expert for clarification.