SAT / ACT Prep Online Guides and Tips

Full Analysis of ACT Grammar Rules: Which Are Most Important?


When you are planning your study approach for ACT English, it’s important to know where your time is best spent.

Which grammar rules are really the most important to learn? What can help you make the greatest improvement to your score?


What kind of questions are on ACT English?

ACT English is a passage based test. There are 5 multi-paragraph passages and 75 questions to go with them.

The makers of the ACT break the test down into two main sections: Usage and Mechanics questions and Rhetorical Skills.


Usage and Mechanics covers questions about punctuation (including internal and end of sentence punctuation and avoiding ambiguity), grammar and usage (including subject-verb agreement, pronoun-antecedent agreement, verb formation, pronoun case, comparative and superlative adjectives and adverbs, and idiomatic use), and sentence structure (including modifier placement and relationships between clauses).

In the past, these questions have made up about 53% of the questions on the test.


The second main category is Rhetorical Skills. These questions will ask about strategy (including understanding when to add or delete information and how to best revise writing for a certain audience), organization (including choosing effective openings, transitions, and conclusions), and style (including choosing correct words, tone, style, and avoiding wordiness).

Also grouped with Rhetorical Skills are questions that ask about the author’s goal. These questions test your ability to recognize main ideas and understand what the passage is about, and understanding the scope of the passage.

These questions usually compose about 47% of the questions on the test.




Since the most recent updates to the ACT, the test makers are not sticking as strictly to these percentages, but they are still good guidelines.


What concepts are tested? And why should you care?

Almost as predictable as the question types are the grammar and style rules that ACT English will test you on.

ACT English heavily favors a few main grammar and style rules, and lightly touches on a multitude of others.


Why should this matter to you?

This means that especially if you are aiming for a mid-range score, you should focus your studying on the main grammar and style rules that are covered.

But if you are aiming for a high score, you should make sure you know all the concepts listed here. Since ACT English has so many questions, even concepts that appear a low percentage of the time will almost definitely be featured and could affect your score.


How did I find this out?

I analyzed over 500 ACT English questions from seven official ACT tests that have been given in the past and wrote down the grammar and style concepts tested in each.

Usually, it was easy to find the answer to a question just by knowing one style or grammar rule. But a couple of questions required knowledge of more than one rule. For these questions, I counted them for both concepts.


And the winners are…


Usage and Mechanics

For usage and mechanics questions, the overwhelming winner of the frequency test is correctly forming and joining sentences at 20.5% of the grammar questions. This covers all the concepts involved in understanding what a correct sentence is, including both fragments and run-ons. This topic also covers correct use of semicolons in joining sentences.

Not far behind in second place are questions dealing with correct uses of commas, dashes, and colons. These questions make up 17.7% of the grammar questions.

Following in third and fourth places are correctly used non-essential clauses and relative pronouns with 10.2% of the questions, and correct verb tense and form, with 9.6% of the grammar questions. This topic involves, among other things, knowing what tense is necessary, and forming the tenses correctly.

So, if you master these four concepts, you will have all the information you need to answer almost 60% of the grammar questions on ACT English.


Here is the full breakdown

This is my analysis of the most commonly-tested grammar concepts on ACT English, along with brief explanations of what each grammar rule means.




#1: Correct Sentence Formation: 20.5%

  •         Recognizing fragments
  •         Recognizing run-ons, including comma splices
  •         Joining sentences correctly
  •         Incorrectly used semicolons


#2: Use of commas, dashes, and colons: 17.7%

  •         No comma between subject and verb
  •         No comma before or after preposition
  •         When to use commas to separate adjectives
  •         No comma between adjective and noun
  •         Commas used after introductory words
  •         No commas between compound subjects or compound objects
  •         No commas around emphatic pronouns
  •         Colons used for a list or explanation
  •         Dashes used with non-essential clauses, as intro for a list, and with a deliberate pause


#3: Correctly formed non-essential clauses and relative pronouns: 10.2%

  •         Non-essential clause must be surrounded by commas
  •         Correct use of which vs. that; who vs. which; who vs. whom


#4: Verb tense and form: 9.6%

  •         Correct and consistent tense usage
  •         When to use past tense instead of past participle
  •         Past participle needs a helping verb
  •         Incorrectly formed past participle
  •         Will vs. would
  •         When to use gerund and when to use infinitive


#5: Misplaced and dangling modifiers and word placement: 9.2%

  •         Descriptive phrases must be next to the word they describe.
  •         Would a word make more sense elsewhere in the sentence?


#6: Apostrophe use: 7.5%

  •         Correct formation of plural nouns
  •         Correct formation of possessive form of nouns
  •         Common contractions and their meanings (such as “it’s”)


#6: Pronoun Use: 7.5%

  •         Consistent use of pronouns
  •         Pronoun-antecedent agreement (including singular or plural pronouns)
  •         Pronoun case
  •         Present and clear antecedents


#8. Idioms: 5.1%

  •         Idiomatic use of prepositions


#9: Parallel Structure and Word Pairs: 4.1%

  •         Use of matching prepositions
  •         Items in a list match
  •         Such as neither…nor, either…or, not only…but also, from…to, as…as


#10: Subject-Verb Agreement: 3.8%

  •         Singular subjects need singular verbs; plural subjects need plural verbs
  •         Subject – non-essential clause – verb construction
  •         Subject – prepositional phrase – verb construction
  •         Verb before subject


#11: Adjectives vs. Adverbs: 2.4%

  •         Adjectives are used to describe nouns
  •         Adverbs are used to describe adjectives, adverbs, and verbs
  •         Correct use of the comparative and superlative forms


#11: Comparison words: 2.4%

  •         Correct use of comparison words such as more/less than, less vs. fewer, much vs. many, and that of/those of


Rhetorical Strategy

These questions are based on making the passages more smooth and logical to read. As in the grammar section, the ACT heavily favors some rules over others.


The big winners for Rhetorical Strategy are…

Logical transitions. Unsurprisingly, in a section all about making passages more logical, transitions reign supreme. Over 18% of the questions will test your ability to create logical bridges within and between sentences and paragraphs.

In second place is adding information with 16.7%. These questions test your ability to see if new information is relevant to the paragraph in question, and also ask students to explain how the paragraphs are changed by the addition of new information.

And tied in third with 15.5% each are conciseness and replacing and re-wording information. Similar to the concepts above, replacing information questions ask student to tell if information is relevant to the paragraph in question, and if not, to replace it with different information. Conciseness questions test students’ abilities to see when the author has been unnecessarily wordy. Repetitive words, circular talking, and the passive voice are all put to the test in these questions!


Let’s break it down completely




#1. Logical Transitions: 18.4%

  •         Includes transitions within sentences, between sentences, and between paragraphs
  •         Transition words make logical sense for context


#2. Adding Information: 16.7%

  •         Determining if new information is relevant to paragraph
  •         Understanding why new information is relevant


#3. Re-wording or Replacing Information: 15.5%

  •         Replacing a word or phrase to add a certain emphasis to the passage
  •         Replacing irrelevant information with relevant information


#3. Conciseness: 15.5%

  •         No using repetitive words to describe something
  •         General wordiness
  •         No passive voice when active voice is also correct and shorter


#5. Deleting Information: 11.7%

  •         Is information irrelevant? If so, delete it.
  •         What information would be lost if sentence were deleted?


#6. Diction: 8.4%

  •         Commonly confused words, such as then/than, have/of


#7. Sentence Order/Placement and Paragraph Organization: 6.7%

  •         Does the placement of a sentence make sense in context?
  •         Does one sentence/paragraph logically follow from the last?
  •         Does a new paragraph start with a shift in topic?


#8. Writer’s Goal: 5.4%

  • Recognizing main ideas in the passage
  • Recognizing specific and general passages


#9. Formality: 1.5%

  • Is the phrasing of an answer too casual or formal to match the rest of the sentence?


So What Would a Perfect Test Look Like?




If you took the ACT English and it broke down exactly according to these statistics, here is what you would expect to see:


8 questions on Forming Correct Sentences

7 questions on Commas, Dashes, and Colons

7 questions on Logical Transitions

6 questions on Adding Information

5 questions on Replacing or Re-wording Information

5 questions on Conciseness

4 questions on Verb Tense and Form

4 questions on Deleting Information

4 questions on Non-essential Clauses and Relative Pronouns

4 questions on Dangling and Misplaced Modifiers and Word Placement

3 questions on Diction

3 questions on Apostrophe Use

3 questions on Pronouns

2 questions on Idioms

2 questions on Parallel Structure and Word Pairs

2 questions on Sentence Order/Paragraph Organization

2 questions on Author Goal/Intent

1 question on Subject-Verb Agreement

1 question on Adjectives vs. Adverbs

1 question on Comparison Words

1 question on Formality

….for a total of 75 questions. 

Of course, it’s unlikely that any test will exactly follow these statistics, so don’t be surprised if you see a few extra (or fewer) questions of a certain type!


How Should You Use This Information? 

Now that you know exactly what you can expect to find on ACT English, use this information to guide your studying.

Here’s a study plan that will help you make the most of your study time to give you the best chance of improving your score.

  1. Take a diagnostic test. To do this, you should take a real ACT English test, because it’s best to work with realistic questions. You can find official ACT tests online, or you can get them from The Real ACT Prep Guide.
  2. After taking the test, score it to see how you've done. For every question that you either got incorrect or had to guess on, make a note of why you got it wrong, and what grammar concept it is testing.
  3. Compare your list of grammar mistakes with the “Perfect Test” list above. Which of your mistakes appears highest on the list?
  4. Focus your studying on the concept that is highest on the list. You’re likely to see that kind of question the most, and so mastering that grammar concept will give you the chance to improve your score by a few points.
  5. When you feel confident that you have mastered the highest concept on the list, move on to the next one. Keep working your way down the list.

As you’re taking these steps, you should also consider what your target ACT score is.

For example, if you're just looking to boost a mid-range score (around a 20) a bit higher (a 24), you’ll want to focus on the first 10 – 12 grammar concepts. If you can get these concepts down, you’ll have a great chance of hitting your target score, and you won’t need to worry about many of the less-frequently-tested concepts.

On the other hand, if you're aiming for a high or perfect score, you should pay attention to every grammar and rhetorical point on the list. Missing even a few points could hurt your chances of getting the score you want.


What’s Next?

Now you know exactly what is on ACT English. Use the above links to master each topic.

Know the concepts, but unsure of how to attack the questions? Read the best way to approach ACT English passages.

Before you get studying, read our top 5 secrets to mastering the ACT English.

Not sure if ACT English is for you? Read our comparison of ACT English and SAT Writing to see which is the best fit!



Have friends who also need help with test prep? Share this article!

author image
Mary Ann Barge
About the Author

Mary Ann holds a BA in Classics and Russian from the University of Notre Dame, and an MA from University College London. She has years of tutoring experience and is also passionate about travel and learning languages.

Get Free Guides to Boost Your SAT/ACT
100% Privacy. No spam ever.

Ask a Question Below

Have any questions about this article or other topics? Ask below and we'll reply!