Sentence Construction
What is a sentence?

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.

What does it take to make a sentence?

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.

Here's a basic sentence diagram. The subject is on the left and the verb is on the right.

Sentence Diagramming - 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. Here is a diagram of a very short sentence. 

Here's a basic sentence diagram.

Flowers grow.

Here is a diagram of a very long sentence. This is 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.

Sentence Diagram of the Preamble

We the people of the United States, in order to form a more perfect Union, establish justice, insure domestic tranquility, provide for the common defense, promote the general welfare, and secure the blessings of liberty to ourselves and our posterity, do ordain and establish this Constitution of the United States of America.  

  • The complete subject contains all of the words that tell us whom or what a sentence is about.

  • The complete predicate contains 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.

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 and complex sentences.) However, you can also find yourself with a run-on sentence. Click on that link to learn more about them and how to use proper sentence construction to fix them.

Do you understand sentence construction now? I sure hope so! 

Hello! I'm Elizabeth O'Brien, and my goal is to get you jazzed about grammar.

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Other Helpful Resources

I hope this lesson helped you learn about sentences and basic sentence diagramming!

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