1.for seprating independent clauses which are not joined by coordinating conjunctions (remember the acronym "FANBOYS" to recall the most important coordinating conjunctions : for , and , nor , but , or , yet , so.)
2.for separating Items in a series that contain comma.
Example : I visited London , England ; Prague , Oklahoma
3.when your sentence contains sentence connectors , like : nevertheless , therefore , thus , etc.
note : when you have sentence connectors , there are 4 ways to use punctuations
- She did not study well ; therefore , she didn't pass the test
- She did not study well . therefore , she didn't pass the test
- She did not study well . she , therefore , didn't pass the test
- She didn't study well . she didn't pass the test ,therefore.