Checking for Run-on Sentences (The Time Grammar Fell in Love with Math)

I started last week’s post (which became this week’s post because it took me a while) by mentioning that clients frequently ask me about run-on sentences. I didn’t address run-ons last week, but I promised I would. I wanted to talk about verbs first because verbs are fundamental to clauses.

What’s a clause?

A clause is equal to a grammatical thought. Sometimes a sentence can contain only one clause. (Look at the sentence you just read for an example.) Other times, a sentence can contain multiple clauses, as this one does.

The official definition of a clause is grammatical unit that contains a subject, a verb, and other, related information. A subject is the person or thing–including an intangible thing–that completes the primary action in the clause. Looking for verbs is the easiest way to find a clause.

Use verbs to look for clauses.

The general rule of thumb is that each clause can only have conjugated verb. There aren’t really any exceptions to this rule, but there are some instances that feel like exceptions, which I’ll go over later.

So, to check for run-on sentences, start by finding the verbs with time markers. (Here’s the link to my previous post in case you’d like some pointers.) The most basic sentence consists of a single clause, including a single conjugated verb. If you find more conjugated verbs in your sentence, make a mental note of how many verbs you find, and get ready to do some very basic math.

Next, look for conjunctions.

Each additional clause needs a conjunction to attach it to the sentence. The math is simple: count the clauses and subtract one; that’s the number of conjunctions you need to find. The difficult part is remembering all of the conjunctions that you can look for.

Coordinating conjunctions are the most basic conjunctions. There are only seven of them: forandnorbutoryet, and so.

Subordinating conjunctions have a slightly more complicated set of rules, the basics still apply. These words are also allowed to add a new clause to a sentence. These include asalthoughafterwhilewhenwheneveruntilunlessbecausebeforeifsince, and so that. When I taught middle school, my class had an AAAWWWUUBBISS chant that we repeated daily for a month. Some kids were insanely proud of their ability to say the whole thing.

Relative pronouns are more complicated still, but again, the same rules apply. Relative pronouns begin relative clauses or noun clauses. The relative pronoun connects the relative clause to the rest of the sentence (just like coordinating and subordinating conjunctions) and stands in for one part of the clause. The relative pronoun won’t ever stand in for the verb, though. So, you can keep checking for conjugated verbs as a foolproof method for counting the clauses in your sentence. Look for these words to help you identify relative pronouns: thatwhichwhicheverwhat, whowhosewhoeverwherewhereverwhenwheneverhowhowever, and why (and also whyever if you’re writing a British romance or something).


Please note that sometimes words that are conjunctions can also function as other parts of speech. For example, before is a conjunction in this case: I need to get my keys before I go. But it’s not a conjunction here: I left before him. Likewise, that is a conjunction here: I’ve already eaten all of the pie that you gave me. But, it’s not a conjunction here: I’ve already eaten all of that pie.

(I just ate two slices of pie, in fact. Overall it was delicious, but somewhere Paul Hollywood is glaring in my direction. The crust was terrible.)

One more note: sometimes you can have more conjunctions than clauses. In the sentence, I like to bake pies and eat them, too, there are two verbs (bake and eat), but they both have the same subject, I. So, there’s technically one clause. If that confuses you, that’s okay. Just look for verbs and conjunctions. 

Words that aren’t conjunctions

A common mistake is for people to believe they’ve followed all of the rules, matching their clauses, conjunctions, and conjugated verbs, but then use a word that’s not a conjunction. Watch out for the words however and therefore. No matter how badly these words would like to be conjunctions, they are not conjunctions. They cannot hold two sentences together.

Sometimes, punctuation works, too.

Sometimes you don’t need conjunction at all because you’ve used punctuation to connect the two clauses. A comma doesn’t work to connect two clauses, but a semicolon, a long dash (called an em dash), a set of parentheses, or a colon does work.

How do I find run-ons?

If you have a very short paper, you might be able to count the verbs and the conjunctions in every sentence. For longer documents, that really isn’t feasible.

Instead, start by looking for sentences that span more than a line. If you have too many of those, increase the number of lines; maybe begin by looking for sentences that take up two or three lines of text. Then, a sentence at a time, count the conjugated verbs. Count the conjunctions. Compare the two numbers.

To fix run-on sentences, add more conjunctions or add punctuation. The easiest fix is to stick a period in there.

Image of the previous three paragraphs with the verbs and conjunctions highlighted.

One more disclaimer

I’ve seen dissertation committee members mark grammatically correct sentences as run-on sentences. Even if the sentence isn’t technically a run-on sentence, it needs to be fixed if your committee member says so. Simply make it shorter and remember that your professor’s job is to be an expert in their field, not an expert proofreader.

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