Perfect grammar isn't the goal. Communication is. But certain grammar mistakes cost marks consistently, and they're often the same ones showing up again and again in student essays. This guide covers the errors that markers actually penalise — and how to fix them.

1. Subject-Verb Agreement

The basic rule is simple: singular subjects take singular verbs, plural subjects take plural verbs. The trouble starts when the subject gets complicated.

Wrong: The list of reasons are unconvincing. Right: The list of reasons is unconvincing.

The subject here is "list" (singular), not "reasons". Prepositional phrases between the subject and verb don't change the agreement.

Wrong: Everyone in the class have finished. Right: Everyone in the class has finished.

Words like "everyone", "nobody", "each", and "every" are always singular — even when they refer to groups of people.

Quick check: Find the main verb. Find its subject. Ignore everything in between.

2. Tense Consistency

Shifting tenses mid-paragraph is one of the most common errors in student essays, and it confuses the reader immediately.

Wrong: She walks into the room and noticed something strange. Right: She walked into the room and noticed something strange.

Pick a tense and stick with it within each paragraph. If you're describing a past event, stay in past tense. If you're making a general argument, stay in present tense.

There are legitimate reasons to shift tense — for instance, when contrasting a past situation with a present one. But the shift should be deliberate, not accidental.

Wrong: Many students used social media daily. It affects their concentration. Right: Many students use social media daily. It affects their concentration.

Quick check: Read each paragraph and underline every verb. Are they all in the same tense? If not, is the shift intentional?

3. Articles: A, An, The

For Cantonese speakers, articles are the single biggest grammar challenge. Cantonese doesn't have articles, so this system feels arbitrary. But it follows rules that you can learn.

Use "the" when the reader knows which specific thing you mean:

• The government should invest more in education. (There's only one government in context.)
• I read the article you recommended. (A specific article, already identified.)

Use "a/an" when introducing something for the first time or referring to any one of a category:

• She wrote a letter to the editor. (One letter, not a specific one.)
• It is an important issue. (One of many important issues.)

Use no article with uncountable nouns and general plurals:

• Education is important. (Not "The education is important" — unless you mean a specific educational programme.)
• Students need feedback. (Students in general, not specific ones.)

Common mistakes:

• "The technology has changed our lives" — should be "Technology has changed our lives" (general concept)
• "She is student" — should be "She is a student"
• "I went to the school" — should be "I went to school" (as a student, not visiting a building)

This takes practice. Don't expect to master it from reading a guide — but being aware of the pattern helps you catch errors when proofreading.

4. Run-on Sentences and Comma Splices

A run-on sentence joins two complete thoughts without proper punctuation. A comma splice does the same thing but with just a comma.

Comma splice: Social media is addictive, many students spend hours on it daily. Run-on: Social media is addictive many students spend hours on it daily.

Both are wrong. Here are four ways to fix them:

1. Full stop: Social media is addictive. Many students spend hours on it daily.
2. Semicolon: Social media is addictive; many students spend hours on it daily.
3. Conjunction: Social media is addictive, and many students spend hours on it daily.
4. Subordination: Because social media is addictive, many students spend hours on it daily.

Option 4 is often the strongest choice — it shows the relationship between the ideas and demonstrates grammatical range.

Quick check: If you can split a sentence into two complete sentences at the comma, you probably need a conjunction, semicolon, or full stop instead.

5. Parallel Structure

When you list items or make comparisons, each element should follow the same grammatical pattern.

Wrong: The school encourages reading, to write regularly, and being active in sports. Right: The school encourages reading, writing regularly, and being active in sports.

Wrong: This policy is not only expensive but also it causes confusion. Right: This policy is not only expensive but also confusing.

Parallel structure matters most in essays because you're constantly comparing ideas, listing reasons, or presenting arguments. Inconsistent structure makes your writing feel clumsy, even if the reader can't pinpoint why.

Quick check: When you write a list or use "both...and", "not only...but also", or "either...or", check that each element matches in form.

6. Active vs Passive Voice

Neither is inherently wrong. The question is which one fits the context.

Active: The government introduced new regulations. Passive: New regulations were introduced by the government.

Use active voice when the doer of the action matters — it's more direct and usually clearer. Use passive voice when the action or result matters more than who did it, or when the doer is unknown.

Good use of passive: Over 500 trees were planted last year. (Who planted them is less important than the result.) Weak use of passive: A decision was made by the committee to reduce funding. (Just say "The committee decided to reduce funding.")

Markers don't penalise passive voice — they penalise unclear or unnecessarily wordy writing. If passive voice makes your sentence longer and harder to follow, switch to active.

Self-Check Checklist

Before you submit an essay, run through these questions:

• [ ] Does every verb agree with its subject? (Watch out for phrases between them.)
• [ ] Is each paragraph consistent in tense? Are any shifts deliberate?
• [ ] Have I used articles correctly? (Check "the" with general concepts, "a/an" with countable nouns.)
• [ ] Are there any sentences I can split into two at a comma? (Possible comma splice.)
• [ ] Do my lists and comparisons use parallel structure?
• [ ] Am I using passive voice because it's appropriate, or just out of habit?

You don't need to check all of these every time. Focus on your own known weaknesses. If articles are your biggest challenge, check those first. If you tend to write run-ons, scan for long sentences with commas.

Practise, Don't Just Read

Reading about grammar helps, but practising it is what makes the difference. The Sentence Drills tool lets you work on specific structures with immediate feedback — so you can build accuracy through repetition rather than memorisation.

And remember: the goal isn't flawless grammar. It's clear, effective communication. A few minor errors in an otherwise well-structured essay won't ruin your score. But repeated basic errors will.

This guide covers grammar issues most relevant to HKDSE Paper 2 and IELTS Writing. For exam-specific marking criteria, see our HKDSE and IELTS guides.