Sentence Structure and Completion

TL;DR

Understanding how sentences are built helps you write clearly and effectively. Every sentence needs a subject and a verb to express a complete thought. You can combine clauses to create more complex sentences, adding detail and flow to your writing.

1. The Mental Model

Think of a sentence as a miniature story. It needs a main character (the subject) doing something (the verb), and sometimes it has supporting details. If you're missing a character or an action, the story isn't complete.

2. The Core Material

What Makes a Sentence Complete?

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At its heart, a complete sentence, or an independent clause, has two main parts: a subject and a verb, and it expresses a complete thought.

• The subject is who or what the sentence is about. It's often a noun or a pronoun.
• The verb is the action the subject performs or the state of being the subject is in.

Example:
* She (subject) reads (verb).
* The cat (subject) is sleeping (verb phrase).

If a sentence is missing one of these or doesn't express a complete thought, it's a fragment.

Combining Sentences with Clauses

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You can make your writing more interesting by combining simple sentences into more complex ones using dependent clauses.

• An independent clause can stand alone as a complete sentence.
• A dependent clause has a subject and a verb but cannot stand alone because it begins with a subordinating conjunction (like because, although, while, since, when) or a relative pronoun (like who, which, that).

You combine them like this:

graph TD
    A["Start with an Independent Clause"] --> B{"Add a Subordinating Conjunction or Relative Pronoun?"};
    B -- Yes --> C["Then add a Dependent Clause"];
    B -- No --> D["Connect Independent Clauses with a Coordinating Conjunction (FANBOYS) or Semicolon"];
    C --> E["Result: Complex Sentence"];
    D --> F["Result: Compound Sentence"];

Types of Sentences

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Knowing these types helps you vary your writing:

• Simple Sentence: One independent clause.
  • The dog barked.
• Compound Sentence: Two or more independent clauses joined by a coordinating conjunction (for, and, nor, but, or, yet, so - FANBOYS) or a semicolon.
  • The dog barked, and the cat ran away.
• Complex Sentence: One independent clause and one or more dependent clauses.
  • Because the dog barked loudly, the cat ran away.
• Compound-Complex Sentence: Two or more independent clauses and one or more dependent clauses.
  • Because the dog barked loudly, the cat ran away, and the birds flew into the trees.

Punctuation Matters

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• Use a comma before a coordinating conjunction that joins two independent clauses (in a compound sentence).
• Use a comma after a dependent clause that comes before an independent clause.
• Don't use a comma if the dependent clause comes after the independent clause (usually).

3. Worked Example

Let's take a few simple ideas and build them into different sentence structures.

Original ideas:
1. The rain fell.
2. The streets became slick.
3. Drivers slowed down.

Simple Sentence:
The rain fell. The streets became slick. Drivers slowed down.

Compound Sentence:
The rain fell, and the streets became slick; drivers slowed down.

Complex Sentence:
Because the rain fell, the streets became slick, and drivers slowed down. (Here, "Because the rain fell" is the dependent clause, "the streets became slick" is an independent clause, and "drivers slowed down" is another independent clause being coordinated with "the streets became slick" by 'and'.)

Compound-Complex Sentence:
Although the rain fell, the streets became slick, and most drivers slowed down quickly. (Here, "Although the rain fell" is dependent. "the streets became slick" is independent. "most drivers slowed down quickly" is also independent, connected by 'and'.)

4. Key Takeaways

• Every complete sentence needs at least a subject and a verb to form an independent clause.
• An independent clause expresses a complete thought and can stand alone.
• A dependent clause has a subject and verb but can't stand alone; it needs an independent clause.
• Combine independent clauses with FANBOYS conjunctions or semicolons for compound sentences.
• Use subordinating conjunctions or relative pronouns to link dependent and independent clauses for complex sentences.
• Punctuation (especially commas) is crucial for clarity when combining clauses.

Common Mistakes to Avoid:
- Sentence Fragments: Leaving out the subject or verb, or having only a dependent clause.
- Run-on Sentences: Joining two or more independent clauses without proper punctuation or conjunctions.
- Comma Splices: Using only a comma to join two independent clauses without a coordinating conjunction.
- Overuse of Simple Sentences: Making your writing sound choppy and immature by not varying sentence structure.

5. Now Try It

Take these three simple sentences: "The bell rang. The students packed their bags. They left the classroom." Your task is to rewrite these three ideas into one compound-complex sentence. Focus on using appropriate conjunctions and punctuation to connect them smoothly. What success looks like: You'll have one well-punctuated sentence that clearly expresses all three original ideas using a mix of independent and dependent clauses.