Sentence Construction

You use sentence construction every day, but have you ever thought about what exactly a sentence is?

A sentence is a group of words that expresses a complete thought.

In order to express a complete thought, every sentence must have two parts.

1. Subject (someone or something)

2. Predicate (what the someone or something is being or doing)

That's it! A sentence is just someone or something being or doing something. Simple, huh?

When we diagram sentences, you can always see those two basic parts. The stuff on the left side of the vertical line is the subject and the stuff on the right side of the line is the predicate.

Subjects & Predicates

Sentence diagramming is a visual way to show how the words in a sentence are related. Sentence diagrams will help you understand sentence construction.

Making sentence diagrams feels more like completing a word game than it feels like working on grammar.

You saw in the picture above how the basic diagram of a sentence works. The subject and verb go on a horizontal line and a vertical line divides them.

This is true of the very simplest type of sentence and the most complex type of sentence.

The picture below shows you a diagram of the Preamble to the United States Constitution.

It's just one sentence, and it's pretty complicated, but notice that in the upper left corner, you can see the vertical line dividing the subject and the predicate.

  • Complete Subject = All of the words that tell us whom or what a sentence is about

  • Complete Predicate = The verb and all of the words that modify or complete it

Don't worry too much about those things now. Just focus on the fact that even really complicated sentences are divided between the subject and the predicate!

Learn more about diagramming sentence with these FREE sentence diagramming exercises.

Sentence Construction &
Sentence Fragments

Some groups of words don't have what it takes to be a complete sentence.

If a group of words is missing one of those two key elements we talked about (subject + predicate), it is a sentence fragment. A sentence fragment is a group of words that does not express a complete thought.

When you read a sentence fragment, you are left wondering whom or what the sentence is about or what happened in the sentence.

You can change a sentence fragment into a complete sentence by adding the missing information.

Sentence Fragment Sentence
in the butter
My glasses fell in the butter!
early this morning
I awoke early this morning.
running across the field
I saw you running across the field

Sentence Construction &
Run-On Sentences

Some groups of words have more than one of those two essential elements that we talked about.

Grammatically speaking, that can be perfectly legit. (Check out compound sentences.) The trouble comes in if the group of words is not punctuated properly.

Those groups of words are called run-on sentences. Click on that link to learn more about them and how to use proper sentence construction to fix them.

Test Yourself

Do you understand sentence construction? Use this grammar quiz on fragments and run-on sentences.

You'll find everything you need to test yourself or your students.

If you want to teach or learn grammar the easy way, then follow a step-by-step program that clearly lays everything out for you and allows you to move at your own pace. The Get Smart program is presented in a logical sequence, so it's not an overwhelming mishmash of information. Before you know it, you'll be a grammar and sentence diagramming pro!

The whole program is online, so you have instant access to these lessons and videos. It's easy and fun. You can get it at
Keep learning and have fun!

Elizabeth O'Brien is the creator of the Grammar Revolution step-by-step grammar and sentence diagramming programs. Her programs are guaranteed not only to teach you grammar, but also to give you more confidence in your communication skills.

To get your free Parts of Speech guide and receive Elizabeth's bi-weekly articles on improving your grammar and having fun with sentence diagramming, enter your email address and name below right now.

First Name

Don't worry — your e-mail address is totally secure.
I promise to use it only to send you Diagram It.

Understand sentence construction? Go back to sentence structure.

Back to English Grammar Home Page