You paid attention in school. My wife’s friend did not.I do understand the usage of semicolons and colons. Over time I learned how to not only explain them to students but to also ensure they could use them correctly. On forums, I am less precise with my grammar - I blame it on my thumbs.
Here's an example in case anyone is interested.
Independent Clause; conjunctive adverb being used as a conjunction, In the dependent clause.
My mother bought me a car; however, I bought a car on Monday.
Independent clauses are combinations of subjects and predicates that can stand as a complete thought.
In the example above, mother is the subject and bought is the predicate in the first part of the sentence and I is the subject and bought is the predicate in the last part of the sentence. The two parts each could stand as a complete thought if spoken by themselves.
My mother bought me a car.
I bought a car on Monday.
One way to join two Independent Clauses is as in the example with the semicolon.
It's been awhile, but I think that is the gist of it.
My college English prof taught me “to each their own” is not proper English. I paid attention as well.