Lesson 1: Sentence Structure & Clarity | Writing & Grammar

Warm-up

Why Sentence Structure Matters

Every piece of writing — an email, an essay, a message — is built from sentences. If your sentences are unclear, your entire message is unclear.

The good news: there are only a few sentence types in English, and once you understand them, you can write with clarity and confidence in any situation.

In this lesson, you'll learn the difference between simple, compound, and complex sentences — and discover how to spot and fix the most common sentence errors that make writing look unprofessional.

Key Concepts

Sentence Types & Errors

Click each card to see the definition and an example.

Simple Sentence

One subject + one verb = one complete thought

"The report is ready." One independent clause. Clear, direct, and effective.

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Compound Sentence

Two clauses joined by FANBOYS

"The report is ready, but we need more data." FANBOYS: for, and, nor, but, or, yet, so. Always use a comma before the conjunction.

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Complex Sentence

Main clause + dependent clause

"Although the report is ready, we need more data." Connectors: because, although, when, if, while, since, after, before.

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Run-on Sentence

⚠ Two sentences jammed together

"The report is ready we need more data." Fix: add a period, semicolon, or conjunction. This is a serious writing error.

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Fragment

⚠ An incomplete sentence

"Because the report is ready." This has no main clause. Fix: attach it to a complete sentence or add a main clause.

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Comma Splice

⚠ Two sentences joined by only a comma

"The report is ready, we need more data." Fix: add a conjunction after the comma, use a semicolon, or make two sentences.

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Parallel Structure

Matching grammatical forms in a list

Wrong: "She likes reading, to swim, and cooking." Right: "She likes reading, swimming, and cooking." Keep the same form.

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Active vs. Passive Voice

Who does the action?

Active: "The team wrote the report." Passive: "The report was written by the team." Active is usually clearer and stronger.

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Key Phrases

Connectors by Function

Use these connectors to combine sentences and show the relationship between ideas.

Addition

Adding more information

and, also, furthermore, in addition, moreover. "The design is clean, and it loads quickly."

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Contrast

Showing a difference

but, however, although, on the other hand, yet. "The design is clean, but the code needs work."

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Cause & Effect

Explaining why or the result

because, since, therefore, so, as a result. "The server crashed because traffic spiked."

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Time & Sequence

Showing order or timing

when, while, after, before, then, first, finally. "After you save the file, send it to the team."

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Sample Writing

Draft vs. Revised

Compare these two versions of the same paragraph. The draft has run-ons, fragments, and comma splices. The revised version fixes each error.

✍️

Project Update Email

Before and after editing for sentence structure

✗

The project is behind schedule we lost two team members last month, the client wants an update. Because they are concerned. We need to meet this week I think Thursday works best the meeting room is available.

⚠ Contains: 1 run-on, 1 comma splice, 1 fragment, and another run-on. Confusing and unprofessional.

✓

The project is behind schedule because we lost two team members last month. The client wants an update since they are concerned. We need to meet this week, and I think Thursday works best because the meeting room is available.

✅ Each sentence is complete and clear. Uses connectors (because, since, and) to show relationships between ideas.

Pattern Spotlight

The "One Idea Per Sentence" Rule

When a sentence goes beyond about 25 words, consider splitting it. Long sentences are not automatically sophisticated — they're often just confusing. Clear = professional.

💡 When to Split a Sentence

Too Long	Better	Why
"The team completed the project on time despite the fact that two members were absent and the client had changed the requirements twice during the final week."	"The team completed the project on time. This was impressive because two members were absent, and the client had changed the requirements twice during the final week."	Split at the logical break. Each sentence has one main idea.
"I will attend the conference which is being held in London next month and I hope to learn about new marketing strategies that can help our company grow."	"I will attend the conference in London next month. I hope to learn about new marketing strategies that can help our company grow."	Two separate ideas (attending + learning) work better as two sentences.

Remember

Long does not equal sophisticated. Clear equals professional. When in doubt, split.

💡

Pro Tip

Read your writing aloud. If you run out of breath before reaching a period, the sentence is too long. Your lungs are a surprisingly good grammar checker. This simple technique catches run-on sentences, awkward phrasing, and missing punctuation that your eyes might skip over when reading silently.

Practice

Test What You've Learned

Complete these exercises to practise identifying and fixing sentence structure problems.

Multiple Choice Exercise 1 of 4

Which of these is a run-on sentence?

The meeting was productive, and we agreed on next steps.

Although the meeting was long, it was productive.

The meeting was productive we agreed on next steps.

The meeting was productive.

🎉

Correct! Option C has two complete sentences with no punctuation or conjunction between them. Fix it with a period, semicolon, or by adding ", and".

💡

Not quite. The run-on is C: "The meeting was productive we agreed on next steps." Two complete thoughts are jammed together without any punctuation or conjunction.

Fill in the Blank Exercise 2 of 4

Add a connector to combine these sentences: "The design looks great, ___ the code needs improvement."

The design looks great, the code needs improvement.

🎉

Excellent! A contrast connector like "but" perfectly shows the opposing relationship between the two ideas.

💡

Almost! You need a contrast connector here. The best options are "but", "however", or "yet" — since the two ideas oppose each other.

Multiple Choice Exercise 3 of 4

Which version is clearer?

The new policy which was introduced last month by the management team in order to improve employee satisfaction and reduce turnover rates has been well received by most departments.

The management team introduced a new policy last month to improve employee satisfaction and reduce turnover. Most departments have received it well.

🎉

Perfect! Version B splits one long sentence into two clear ones. It uses active voice and gets to the point faster. Same information, much easier to read.

💡

Not quite. Version B is clearer. It splits the long sentence into two focused ones and uses active voice instead of passive. Remember: clear = professional.

Word Order Exercise 4 of 4

Combine these two ideas into one compound sentence:

excellent

was

The

but

quality

late

the

report

was

🎉

You got it! "The report was late, but the quality was excellent." A compound sentence using "but" to show contrast between the two ideas.

💡

Close! The correct order is: "The report was late but the quality was excellent."

Key Takeaways

3 sentence types: simple (one clause), compound (FANBOYS), complex (dependent clause).

3 common errors: run-on sentences, fragments, and comma splices. Learn to spot and fix them.

FANBOYS = for, and, nor, but, or, yet, so. Use these to create compound sentences.

One idea per sentence. If it's over 25 words, consider splitting it.

Use connectors to show relationships: addition, contrast, cause, and time.

Read aloud to check. If you run out of breath, the sentence is too long.

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