The Complex Sentence

This post is a part of the essential toolkit of grammar knowledge I feel all kids should have. The following parts can be found here: the subject, the predicate, the simple sentence, the compound sentence, the complex sentence, sentence fragments, and run-on sentences.


Complex sentences are aptly named because they are more complicated than simple sentences and the limited number of options for writing compound sentences.

The most accessible way to understand the structure of a complex sentence is to use the word because. All proper sentences that use the word because are complex sentences. Here’s an example.

I am tired today because I was playing video games too late last night.

Because the apples were on sale, Jawad purchased an extra few.

And yes, you saw that correctly. There is a sentence which starts with Because! It is possible, and we should be teaching our students that they can start sentences with Because so long as they finish them. Because is a powerful and useful word, and it’s very quickly acquired by English language learners.

But the issue with Because highlights the importance of our students understanding what makes a complete sentence. They can handle it, but they do need an understanding of what a complex sentence is. So here we go. Here are two formulas for the complex sentence:

1 subject + 1 predicate AAAWWUBBIS 1 subject + 1 predicate

or

AAAWWUBBIS 1 subject + 1 predicate, 1 subject + 1 predicate

I take it for granted students will capitalize the first word and complete the sentence with a period, question mark, or exclamation mark, so I won’t include them in the formula.

What the heck is AAAWWUBBIS. I like the acronym because it’s a whole lot easier to remember than the proper term which is subordinating conjunctions. AAAWWUBBIS refers to the most common words used to make complex sentences: after, although, as, when, while, until, because, before, if, since.

I can never remember how to spell AAAWWUBBIS or all of the words contained in the acronym, but it’s easy to say. And when students can plug in the kind of words that AAAWWUBBIS are, such as after, it’s easy for them to figure out the rest.

Here are some complex sentences in action with the predicates underlined and the AAAWWUBBIS in bold.

After we finish the softball game, we usually grab something to eat at Tim Horton’s.

Mum‘s not going to be very happy if you don’t clean up your room.

AAAWWUBBIS doesn’t contain all the words needed to make complex sentences, but it does contain the most common ones.

But there is one more thing to know about complex sentences. You can teach it using the proper vocabulary, which might be more appropriate for high school or adult students, but then you can get away with this explanation using the rules of a simple sentence.

Let’s look at the following example.

I’ll come to the party if you pick me up.

In a complex sentence, one side of a sentence can stand on it’s own if it is a simple sentence. This side is called the independent clause, which is just a fancy way of saying a subject and predicate that together can make a complete thought. in other words, a simple sentence. I might just tell my students to identify “the strong one”. In this sentence I’ll come to the party is the strong part because if I slap a period on the end, it becomes a complete sentence with a complete thought.

If I try to do that with the other side, the dependent clause, or the weak side, it won’t work.

If you pick me up.

This fails the complete thought test even though this has both a subject and a predicate.

Sounds complicated? It’s not really. Just try to hold that thought in your mind… If you pick me up. Most of us can’t, and for those students who claim they can, tell them to add the rule that simple sentences should have no AAAWWUBBIS attached. Some students just like their rules.

If you can reliably identify and write a simple, compound, or complex sentence, then you have the foundations for adding all kinds of variations to your writing repertoire. We don’t want our students, especially our ELLs, to blindly blunder their way through their writing. Tense, plurals, and spelling, are complicated for language learners, but if the structure of their sentences are sound, then any errors in those aspects of the language will impede, but not totally obstruct, their meaning.

Look at the following examples with good sentence structure but incorrect use of verbs.

She go to school everyday, but he will only go sometime.

If you jumping, I jumping too.

Now look at the following examples.

Sleeping outside under the stars.

When I am feeling low.

These sentences are all incorrect, but notice that because the second two examples mess with the structure of a simple and complex sentence, they’re hard to understand. The first two are like having stains on your shirt. The second two are like missing an item of clothing.

This brings us to the last two important pieces of grammar knowledge that all students should know: sentence fragments, and run-on sentences.

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