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.

They are seven little words: for, and, nor, but, or, yet, so. And we only ever really use four of them. You figure out which four those are….Alright, they are: and, but, or, so.

They’re really easy to spell, and I believe they have their equivalences in most other languages.

I teach these little words to my students with the acronym FANBOYS, but their correct name is coordinating conjunctions. They allow for two simple sentences to be joined together to make a compound sentence. (They also can be used to combine words or phrases, but let’s set that aside for a moment.)

Remember that a simple sentence is one subject and one predicate that make up a complete thought.

Raymond is nice.

A compound sentence joins two simple sentences together. Like this:

Raymond is nice. His brother isn’t.

Raymond is nice, but his brother isn’t.

While it can be a matter of taste to place that comma in the middle when both parts are short, I think it’s a good idea to get students in the habit of adding it. And that’s because we can use a FANBOYS in simple sentences, like this.

Her name is Susy or Sally.

This is a simple sentence because it has just one subject and one predicate. It doesn’t need a comma before or.

Compound sentences can also join two simple sentences through the use of a semi-colon, like this.

He cooks; she cleans.

I won’t go into great detail about why you might forgo using a FANBOYS when writing a compound sentence, but if the connection between the two parts of the sentence is clear, it can be redundant to add a comma and an and.

To conclude, the formula for compound sentences is:

1 subject + 1 predicate [, FANBOYS/;] 1 subject + 1 predicate

So there you have it. It shouldn’t take much longer than the time it took to read this for students to be introduced to the topic. The next step is to get them to practice writing compound sentences.

For more practice on forming and identifying compound sentences try these exercises over at Khan Academy.

Finally, if you have time, read the next essential bit of grammar knowledge that I think all students should know: complex sentences.