Why These Mistakes Matter

After twenty years of marking student essays in Hong Kong, certain patterns become impossible to ignore. The same mistakes appear across Form 4 essays and university applications, across HKDSE practice papers and IELTS attempts.

These aren't obscure grammar rules that only pedants notice. They're structural and stylistic issues that cost marks and make essays harder to read.

The good news: once you're aware of them, they're not difficult to fix.

1. Run-on Sentences and Comma Splices

This is the most common issue I see. Students connect independent clauses with commas when they should use full stops, semicolons, or conjunctions.

The Problem

The government should invest more in education, this will benefit society in the long run, students will have better opportunities.

This sentence contains three separate ideas, each deserving its own sentence. Jamming them together with commas creates a grammatical error called a comma splice.

The Fix

You have several options:

The government should invest more in education. This will benefit society in the long run, as students will have better opportunities.

Or use a semicolon when the ideas are closely related:

The government should invest more in education; this will benefit society in the long run.

How to Spot Comma Splices in Your Writing

Read each sentence aloud and pause at commas. If the part before the comma is a complete thought and the part after is also a complete thought, you need a stronger connector.

2. Inconsistent Register

Register means the level of formality in your writing. Academic essays require formal register throughout.

Many students start formally, then slip into casual language when they're explaining ideas or giving examples.

The Problem

The implications of climate change are far-reaching and demand immediate governmental intervention. Basically, if we don't do something soon, we're all gonna be in trouble.

The shift from "governmental intervention" to "gonna be in trouble" is jarring. It undermines the authority of your argument.

The Fix

The implications of climate change are far-reaching and demand immediate governmental intervention. Without decisive action, the consequences will affect every sector of society.

Signs of Informal Register to Avoid

• Contractions — don't, won't, can't (write them out in formal essays)
• Slang or colloquialisms — gonna, kind of, a lot
• Vague generalisations — "We all know that...", "Everyone agrees..."
• Excessive rhetorical questions — one or two for effect is fine; constant questioning undermines authority

3. Weak or Missing Thesis Statements

A thesis statement tells the reader exactly what your essay will argue. It should appear at the end of your introduction and preview all your main points.

The Problem

In this essay, I will discuss the advantages and disadvantages of social media.

This tells me what you'll write about, but not what you'll argue. It's a topic statement, not a thesis statement.

The Fix

While social media offers unprecedented opportunities for connection and information sharing, its negative effects on mental health and productive time outweigh these benefits for most users.

Now I know your position and can anticipate your argument structure: one paragraph on benefits, then paragraphs on mental health impact and time costs.

What Makes a Strong Thesis

A strong thesis statement has three essential qualities:

• Clear position — State what you believe, not just the topic
• Debatable claim — Someone could reasonably disagree with you
• Structural preview — Signal what your main arguments will be

4. Paragraphs Without Topic Sentences

Every body paragraph should begin with a topic sentence that states the paragraph's main idea.

Without one, readers have to work out what the paragraph is about, which slows comprehension and suggests disorganised thinking.

The Problem

Many students use their phones during class. Teachers find this distracting. Studies show that multitasking reduces learning outcomes. Parents often complain about screen time. The school introduced a phone ban last year.

These are all related to phones and schools, but what's the point? The paragraph lacks direction.

The Fix

Mobile phone use in classrooms significantly disrupts the learning environment. Many students check their phones during lessons, which teachers find distracting and studies have linked to reduced learning outcomes. These concerns prompted our school to introduce a phone ban last year, a measure that parents have broadly supported.

The topic sentence ("Mobile phone use in classrooms significantly disrupts the learning environment") tells readers exactly what this paragraph will prove. Everything that follows supports that claim.

How to Write Better Topic Sentences

Your topic sentence should:

• Make a claim — Not just announce a topic
• Connect to your thesis — Show how this paragraph advances your argument
• Be specific — Give readers a clear expectation of what's coming

5. Overreliance on Basic Vocabulary

Using the same simple words repeatedly makes your writing feel underdeveloped.

HKDSE and IELTS markers specifically reward vocabulary range and sophistication.

The Problem

The movie was very good. The acting was good and the story was good. I think everyone should watch this good film.

Four uses of "good" in three sentences. This repetition signals limited vocabulary.

The Fix

The film was compelling from start to finish. The performances were nuanced, particularly the lead actress whose emotional range anchored the narrative. The plot unfolded with satisfying complexity, rewarding attentive viewers with carefully planted details. I would recommend it to anyone who appreciates thoughtful cinema.

Notice how each descriptor is specific and meaningful.

Strategies for Vocabulary Improvement

• Keep a vocabulary notebook — Organised by topic (education, environment, technology)
• Learn words in context — Not from isolated lists
• Practise immediately — Use new words in sentences the same day you learn them
• Read widely — Note how skilled writers vary their word choices
• Use a thesaurus carefully — Check that synonyms fit the context before using them

Common Overused Words to Replace

Replace these weak words with more precise alternatives:

• "Good" → beneficial, effective, valuable, compelling
• "Bad" → detrimental, problematic, inadequate, harmful
• "Very" → extremely, remarkably, significantly (or delete it)
• "Things" → factors, elements, aspects, considerations
• "A lot" → numerous, substantial, considerable, extensive

Using EssayHero to Catch These Mistakes

EssayHero's paragraph-by-paragraph feedback can help you identify these patterns in your own writing.

What the Analysis Checks

• Language criterion — Evaluates vocabulary range and grammatical accuracy
• Organisation criterion — Checks for clear topic sentences and logical flow
• Content criterion — Assesses whether your thesis is clear and well-supported

How to Use the Feedback

Submit a practice essay, read the feedback, and look for recurring issues. If the AI flags the same problem across multiple paragraphs, that's a pattern worth working on.

Questions about essay writing or EssayHero? Email hello@essayhero.app.