Grammatically Correct: The writer's essential guide to punctuation ...

GRAMMATICALLY CORRECT
Subsequently, the negotiations broke down.
In short, the trip was a resounding success.
His feelings were hurt, understandably.
It was my best performance ever, in fact.
The presentation, however, was an embarrassing calamity.
The meeting, therefore, was canceled.
As introductory elements, these words can appear either at the
beginning of a sentence, to link it with an earlier one, or at the
beginning of a second clause, to link it with the first. In the latter
case, separating the clauses with a comma would create the error
known as a comma splice (see page 65), and the reader might
have a fleeting uncertainty as to whether the conjunctive word is a
concluding element to the first clause or the opener to the next.
Accordingly, the stronger separation of the semicolon is needed.
I'd rather have the report by tomorrow; however, Monday will do.
He didn't think he'd have anything to contribute to the meeting; besides,
he wasn't interested in the topic.
Max finally showed up two hours late; understandably, he met with a
frosty reception.
She thought she was early; in fact, she was the last to arrive.
We waited and waited; eventually, we gave up.
No progress was evident; nevertheless, they persevered.
A final comment on the use of these conjunction-like words: Some
are very similar to actual conjunctions. For example:
The argument was going nowhere, so we decided to drop it.
The argument was going nowhere; hence, we decided to drop it.
The apartment was small and dark, but the price was right.
The apartment was small and dark; however, the price was right.
These is essentially no difference in meaning between these pairs
of sentences. The ones with commas tend to look a bit more casual;
the ones with semicolons, a bit more formal. When either way would
do, your choice should depend on the tone of your writing. No single
style is the most appropriate for every situation.
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