Common Sentence Mistakes

C1 · AdvancedCommon Grammar Mistakes

I don't know anything (not nothing), because I was tired, I went to bed (not just 'because I was tired') — mistakes about how a whole sentence is built, not just single words.

What you'll learn

  • English uses only one negative per sentence — 'I don't know anything', not 'I don't know nothing'
  • A sentence fragment is missing an independent clause — a subordinating word like 'because' or 'although' needs a main clause attached to it
  • A dangling modifier describes the wrong noun because the subject it should attach to is missing from the main clause
  • A comma splice joins two complete sentences with only a comma — it needs a conjunction, a semicolon, or a period instead
  • Items in a list or comparison should share the same grammatical form — all nouns, or all -ing forms, not a mix

Whole-sentence mistakes, not word-level ones

This lesson pulls together the sentence-structure mistakes that tend to survive even at an advanced level, because they're about how a whole sentence is put together, not about a single word choice.

Only one negative per sentence

English (unlike many other languages) uses a single negative to make a sentence negative. Adding a second negative word cancels the first one out logically, even though it's clearly not the intended meaning.

"I don't know anything about it. (not: I don't know nothing)"
"She hasn't got any free time. (not: hasn't got no free time)"

Sentence fragments

A subordinating word like 'because', 'although', 'when', or 'which' introduces a dependent clause — it can't stand alone as a full sentence and needs an independent clause attached to it.

"Because I was tired, I went to bed early. (not just: Because I was tired.)"
"A result which nobody had expected. → A result which nobody had expected surprised everyone."

Dangling modifiers

An introductory phrase like 'Running down the street' or 'After finishing the report' needs to describe the subject that immediately follows it. If that subject is missing, the phrase attaches to the wrong thing — often producing an unintentionally funny sentence.

"Running down the street, I saw the bus leave. (not: Running down the street, the bus left — the bus wasn't running!)"

Comma splices and broken parallel structure

Two complete sentences joined only by a comma need a conjunction, a semicolon, or a full stop instead. And items in a list should all share the same grammatical form.

"It was raining, so we stayed inside. (not: It was raining, we stayed inside.)"
"I like swimming, cycling, and running. (not: swimming, cycling, and to run)"

Real English

"Although she disagreed, she stayed quiet."
"Walking into the room, I noticed the lights were off."
"The course covers writing, speaking, and listening."
"The meeting ran late, so everyone left early."

Watch out

✗I don't know nothing about it.
✓I don't know anything about it.

English uses only one negative per sentence — a second negative word cancels the first one out logically.

✗Because I was tired.
✓Because I was tired, I went to bed early.

A subordinating clause needs an independent clause attached to it — it can't stand alone.

✗Running down the street, the bus left.
✓Running down the street, I saw the bus leave.

The introductory phrase must describe the subject right after it — the bus wasn't the one running.

✗It was raining, we stayed inside.
✓It was raining, so we stayed inside.

Two complete sentences joined by only a comma need a conjunction, semicolon, or period.

Real life — Proofreading an email before sending it

"Can you check this paragraph before I send it? Something feels off."

"You've got a comma splice here — 'the deadline moved, we adjusted the plan' needs a conjunction."

"Good catch. Anything else?"

"Just one more — this sentence starts with 'Reviewing the numbers,' but the subject right after it is 'the report,' not you, so it sounds like the report was reviewing itself."

Practice

Exercise 1 · Choose the correct sentence

Which is correct?

Exercise 2 · Choose the complete sentence

Which is a complete sentence, not a fragment?

Exercise 3 · Choose the correct sentence

Which is correct?

Exercise 4 · Choose the correct sentence

Which is correct?

Exercise 5 · Choose the sentence that avoids a comma splice

Which avoids a comma splice?

Exercise 6 · Choose the correct sentence

Which is correct?

Exercise 7 · Choose the complete sentence

Which is a complete sentence?

Exercise 8 · Choose the sentence with parallel structure

Which keeps the list items parallel?

Exercise 9 · Correct the dangling modifier

Correct the dangling modifier: After finishing the report, the printer broke.

Exercise 10 · Correct the sentence fragment

Correct the sentence fragment: Even though the plan was risky.

Exercise 11 · Sort into fragments and complete sentences

Because the flight was delayed.
Because the flight was delayed, we missed the connection.
Which nobody had expected.
A result which nobody had expected.
Although she disagreed.
Although she disagreed, she stayed quiet.

0 / 6 sorted

Quick challenge

Five quick questions to check what stuck.

Question 1 / 5

Score: 0/0

Which is correct?

You learned

  • English uses only one negative per sentence.
  • A subordinating clause needs an independent clause attached — it can't stand alone.
  • An introductory phrase must describe the subject right after it.
  • Join complete sentences with a conjunction, semicolon, or period — not just a comma.

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