Conjunctive adverbs act as transitions between complete ideas by indicating comparisons, contrasts, results, and other relationships. A semicolon and a comma are used together when a conjunctive adverb separates two main clauses.
I wanted to go; however, I was too busy.
Here is a list of common conjunctive adverbs.
The check was far more than the balance; consequently, it bounced.
These things really happened; otherwise, I wouldn't have claimed to have seen them.
In these sentences, the conjunctive adverb may look like a coordinate conjunction (and, or, so, but, for), but it is not as strong as a coordinate conjunction. Therefore, the semicolon is used to link the two main clauses, and the comma is used to set off the conjunctive adverb (really a one-word adverb cluster) from its main clause.
When a sentence shows an unexpected result of another sentence, only a few conjunctive adverbs can be used. The most common ones are probably nevertheless, nonetheless, and still:
Ahmed had the flu and should have stayed home; nevertheless, he still went to work.
*However can also be used to introduce an unexpected result:
Ahmed had the flu and should have stayed home; however, he went to work.
A compound sentence is composed of two or more simple sentences. A compound sentence is used when you want to give equal weight to two closely related ideas. This is called coordination. The following are joining words (coordinating conjunction) used in a compound sentence: FANBOYS
Use a comma before the joining word.
The rain increased, so the officials cancelled the game.
A complex sentence is made up of a simple sentence and a statement (dependent clause) that begins with a dependent word (subordinating conjunction). The following are commonly used dependent words:
The subordinate conjunction has two jobs. First, it provides a necessary transition between the two ideas in the sentence. This transition will indicate a time, place, or cause and effect relationship.
I checked my money before I invited Tom for lunch.
The second job of the subordinate conjunction is to reduce the importance of one clause so that a reader understands which of the two ideas is more important. The more important idea belongs in the main clause, the less important in the clause introduced by a subordinate conjunction.
As Samson blew out the birthday candles atop the cake, he burned the tip of his nose on a stubborn flame.
Burning his nose > blowing out candles.