Argh, run-on sentences (comma splice) galore *bangsheadagainstdesk*
I really don't understand how this is a problem for so many writers:
Each independent clause must be joined by proper punctuation or an appropriate conjunction.
What's an independent clause you ask?
You can think of it as a thought or statement that can stand on its own (grammatically, including at least a subject and a predicate). "It's Monday today." "I like playing football." "Pizza is better than ravioli." "It's colder at night."
If you got two of those (which obviously you get when writing more than any 1 thing) they need to be appropriately connected. 100% of the time a full stop is grammatically correct. You cannot make this mistake if you start at that.
Now,
alternatively, you can use a conjunction to connect independent clauses appropriately. Conjunctions can range from
and, but, so, etc. to
because, after, although, while, etc. to somewhat more complex ones as
either... / or ... and similar. But point is ... you gotta pick one of them when connecting independent clauses.
"It's Monday today
because it's the first day of the week."
"I like playing football,
but I don't like playing hockey."
etc.
This is of course simplified and there's other considerations to be made, but fundamentally it's as simple as that. Instead we get
"I'm moving to my father's house, he's lived here since his divorce from my mom."
"...but my mom got promoted, she had to go to work in France."
"I'm in my last year of high school, I don't speak French."
etc.etc.etc.
Not to much a myriad of other mistakes. Especially with tenses.
Just what the fuck are kids learning in school these days ...
(ps: not all grammar checker will notice run-on sentences, but many will. That being said, they tend to suggest semicolons. Semicolons are appropriate when you want to express statements being very closely related, but they should be rare exceptions in good writing (some would say: don't use them at all). In any case, whenever something suggests a semicolon, you know you got a run-on sentence issue there).