A quick note before we begin: I’m positively elated to have teamed up with Tumblr all-star The YUNiversity for this post! Everybody knows that eye-popping visuals are a great boon to students trying to learn otherwise dry material, and nobody does them better. If you like the illustrations he provided for this post, you simply must make a habit of checking his site every day. He’s amazing.

Ok, now. If you want to understand run-on sentences, first you have to understand the difference between a sentence and a fragment. Both are similar in that they contain a subject and a verb, but a sentence can stand on its own as a complete thought, and a fragment cannot. Fragments seem to end abruptly, and leave you wanting to ask something like “…and then what?” To make things super clear in this post, in the examples below complete thoughts will be in green and fragments will be in brown.#

It’s easier to show this than to try to describe it, so here are some fragments. As you look them over, ask yourself “What is it about these that prevents them from standing alone as complete sentences?”

  • even though his fans booed him
  • when the cows come home
  • because her mother was in jail for grand theft auto
  • while you were sleeping
  • to whomever the taser belonged

None of the above are complete thoughts — they’re the beginnings or the ends of thoughts, but mean very little on their own. On the SAT, if you see a fragment trying to be a sentence all by itself, you have to fix it. Fragments are always wrong on the SAT.

A run-on (or “comma splice,” if you like) is kinda the opposite problem. If you come across a comma that’s separating two complete thoughts, that’s a run-on. Like fragments, run-ons are always wrong and you need to fix them.

A run-on looks like this:
Two complete thoughts separated by a comma? NO ME GUSTA.
To fix a run-on:

USE CONJUNCTIONS.
(FANBOYS: for, and, nor, but, or, yet, so)

WRONG: My father smokes cigars, everything in our house smells like cigars.
RIGHT: My father smokes cigars, so everything in our house smells like cigars.

WRONG: The other day my favorite episode of The Fresh Prince of Bel-Air was on, I didn’t watch it.
RIGHT: The other day my favorite episode of The Fresh Prince of Bel-Air was on, but I didn’t watch it.

WRONG: Corey stayed up until 2:00 AM last night, she’s feeling very tired today as a result.
RIGHT: Corey stayed up until 2:00 AM last night, and she’s feeling very tired today as a result.

USE SEMICOLONS.
(BE CAREFUL!!! On the SAT, semicolons REQUIRE complete thoughts on either side.
If there’s a fragment on one side of the semicolon, it’s wrong.)

WRONG: Make sure your zombie survival hideout is stocked with weapons that can pierce a human skull, the only way to kill a zombie is to destroy its brain.
RIGHT: Make sure your zombie survival hideout is stocked with weapons that can pierce a human skull; the only way to kill a zombie is to destroy its brain.

WRONG: The hardest part of the SAT for many students is its length, the test is almost four hours long.
RIGHT: The hardest part of the SAT for many students is its length; the test is almost four hours long.

WRONG: Yesterday I played laser tag, I won first place three times in a row against a bunch of 14 year olds.
RIGHT: Yesterday I played laser tag; I won first place three times in a row against a bunch of 14 year olds.

BREAK THE KNEECAPS OF ONE SIDE (CLAUSE FIX).
(If one side isn’t a complete thought anymore, problem solved!)

WRONG: Students at Brown University call themselves Brunonians, it’s weird.
RIGHT: Students at Brown University call themselves Brunonians, which is weird.

WRONG: The flashing lights kept me up at night, I had to move the router out of my bedroom.
RIGHT: Because the flashing lights kept me up at night, I had to move the router out of my bedroom.

WRONG: The developers’ commentary in Portal 2 is very enjoyable, however* players should play through the game without it first.
RIGHT: Although the developers’ commentary in Portal 2 is very enjoyable, players should play through the game without it first.

* The word “however” is NOT a conjunction and cannot be used to fix a run-on. If it’s not one of the FANBOYS, don’t use it as a conjunction. Click here for more on words like “however.”

USE A PERIOD.
(In real life, yes of course. On the SAT Sentence Improvement section though, this is never an option. The sentence you’re improving is always going to remain ONE sentence.)

Shall we summarize?

On the SAT Sentence Improvement section, when you see a comma (yes, every time) you must ask yourself:

Read about Dangling Modifiers, Broseph. 

And don’t forget! Whenever you see a semicolon, you must ask yourself:

Think you’ve got all this? Try a drill, brochacho!

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# What we’re really talking about here, if you want to get technical, is the difference between dependent and independent clauses. A dependent clause DEPENDS on something, so it can’t stand on its own. Dependent clauses are fragments. Independent clauses can stand on their own as complete sentences. Every time you see “complete thought” in this post, we’re really talking about an independent clause. As for the color schemeindependent clauses are green, and dependent clauses are brown