Grammar Help

So it all comes down to diction and the syntax is dependent on that?

Would ,and and ; imply the same thing; although, in this particular case due to the context a semi-colon can't be used?

I'm just unsure if anything I write these days is grammatically correct including the above sentences (and this one).

This is something my English teacher told me: A semicolon can be used to join two short sentences that would have otherwise been separated by a period. Perhaps you could use this as a benchmark to decide when to use a semicolon.