You’re sitting there, the clock is ticking, and you’re staring at a sentence about a botanist named Martha who apparently loves her succulents way too much. The underlined portion is just a comma. Or maybe it’s a semicolon. Suddenly, everything you thought you knew about your native language evaporates. That’s the ACT English section for you. It isn’t actually testing if you’re a "good writer" in the creative sense. It’s testing if you can follow a very specific, almost mechanical set of ACT English grammar rules that the test makers at ACT, Inc. obsess over every single year.
Most people blow it. They rely on "ear." They read the sentence in their head and if it sounds like it has a natural pause, they slap a comma in there. Huge mistake. The ACT doesn't care about your "ear." It cares about syntax.
The Comma: The Test's Favorite Trap
Commas are the absolute bread and butter of this exam. If you don't master them, your score is going to tank. Period.
The most frequent error involves the "comma splice." This is when you try to join two independent clauses—full sentences that can stand on their own—with nothing but a measly comma. You can’t do that. It’s grammatically illegal in the eyes of the ACT.
For example, look at this: The hike was grueling, we reached the summit by noon.
Wrong. You have two choices to fix this according to the rules. You can use a period, a semicolon, or a comma plus one of the "FANBOYS" (for, and, nor, but, or, yet, so). If you see a comma standing alone between two big, beefy sentences, it's almost certainly the error.
Then there are non-essential clauses. These are the bits of information that add flavor but aren't necessary for the sentence to make sense. Think of them like appositives.
Mr. Henderson, my eccentric chemistry teacher, accidentally melted a beaker. The part about him being eccentric is extra. You have to wrap that info in "commas-as-handles." If you start the interruption with a comma, you must end it with one. The ACT loves to give you the first comma and see if you’re smart enough to realize the second one is missing four words later.
Semicolons and Colons are Actually Simple
People freak out when they see a semicolon. Don't.
✨ Don't miss: Ariana Grande Blue Cloud Perfume: What Most People Get Wrong
For the purposes of the ACT English grammar rules, a semicolon is literally just a period that didn't go to finishing school. It functions exactly like a period. It separates two complete, independent thoughts. If you can't put a period there, you can't put a semicolon there. It's a binary choice. If you see an answer choice with a period and another with a semicolon in the exact same spot, and the rest of the sentence is identical? Both are wrong. Why? Because they do the same thing, and the ACT won't have two right answers.
Colons are a bit more sophisticated but still predictable.
A colon must be preceded by a full, independent sentence. What comes after the colon can be a list, a single word, or even another sentence that explains the first. But that first part? It has to stand on its own. You can't say: My favorite fruits are: apples, pears, and bananas. That's wrong because "My favorite fruits are" is a fragment. You’d just say: I have three favorite fruits: apples, pears, and bananas.
The "Delete" Button is Your Best Friend
Redundancy is a silent killer.
The ACT prizes "economy of expression." This is a fancy way of saying they hate it when you use too many words. If an answer choice says "annually every year," it's garbage. "Annually" means "every year." Pick one.
Often, the shortest answer is the right one. This isn't a hard-and-fast rule—don't just go through the test circling the shortest line—but if the short version conveys the same meaning as the long, flowery version, the short one wins. The test makers are looking for clarity. They want to see if you can spot when a writer is being repetitive or wordy for no reason.
Verbs, Pronouns, and the Subject-Verb Disconnect
Subject-verb agreement seems like third-grade stuff until they bury the subject under a pile of prepositional phrases.
🔗 Read more: Apartment Decorations for Men: Why Your Place Still Looks Like a Dorm
The box of vintage, hand-painted Christmas ornaments (is/are) in the attic.
A lot of students see "ornaments" and want to pick "are." But the subject is "box." The box is in the attic. The ACT will purposefully put a plural noun right next to the verb to trick your brain. You have to strip the sentence down to its bones. Find the actor, then find the action.
Pronouns are another minefield. "It’s" vs. "Its."
"It’s" = It is.
"Its" = Possession.
It is the opposite of how we use apostrophes with names (like "Dave's bike"). It's annoying, it's counter-intuitive, and it appears on almost every single test. Also, watch out for "who" vs. "whom." Briefly: "who" does the thing, "whom" has the thing done to it. If you can replace it with "he," use "who." If you can replace it with "him," use "whom."
Dashes: The Wildcard
Dashes (specifically em-dashes) are like the Swiss Army knife of ACT English grammar rules. They can do the job of a comma, a pair of commas, or a colon.
- To set off a parenthetical: The pizza—which was cold and soggy—tasted like cardboard.
- To show a sudden break in thought: I was going to go to the mall—but then I remembered I was broke.
- Like a colon: There was only one thing he wanted—revenge.
The trick with dashes is consistency. If you start a parenthetical interruption with a dash, you can't end it with a comma. You have to be consistent. It’s either two dashes or two commas. Mixing and matching is a fast way to lose points.
Transitions and "Logic" Questions
About a third of the English section isn't about grammar at all; it's about rhetorical skills. You'll see questions asking which transition word works best: "However," "Furthermore," "Consequently," or "Similarly."
You have to look at the relationship between the two sentences.
💡 You might also like: AP Royal Oak White: Why This Often Overlooked Dial Is Actually The Smart Play
- Is the second sentence an example? Use "For instance."
- Is it a contradiction? Use "However" or "Nevertheless."
- Is it a result? Use "Thus" or "Therefore."
If you read the two sentences and they're saying the same thing, you don't need a transition like "however." Sometimes the best transition is no transition at all.
Active vs. Passive Voice
While not strictly a "rule" that makes a sentence wrong, the ACT heavily prefers the active voice.
Active: The chef prepared the meal.
Passive: The meal was prepared by the chef.
The active voice is more direct and usually shorter. If you're stuck between two grammatically correct options, look for the one where the subject is actually performing the action rather than having the action performed upon it.
The Importance of Context
You cannot answer ACT English questions in a vacuum. Sometimes the grammar is perfect, but the sentence doesn't make sense in the context of the paragraph. This happens a lot with "Placement" questions, where they ask where a sentence should be moved.
Read the paragraph as a whole. Look for "clue words" like "This discovery" or "That person." If a sentence mentions "this discovery," it better come right after a sentence that describes a discovery. It’s a logic puzzle disguised as a grammar test.
Practical Steps for Score Improvement
Improving your score isn't about reading a grammar textbook from 1950. It's about targeted practice.
- Take a baseline test. Find a real, released ACT from a previous year. Sit down and do the English section in 45 minutes.
- Categorize your mistakes. Don't just look at the right answer. Ask why you got it wrong. Was it a comma splice? Did you miss a non-essential clause? Was it a redundancy issue?
- Drill the "Big Four." Mastery of commas, semicolons, colons, and dashes accounts for a massive chunk of the points.
- Read more. It sounds cliché, but reading high-quality journalism (like The New York Times or The Economist) helps your brain internalize what correct, sophisticated syntax looks like.
- Ignore your "ear" when it fails. If a sentence sounds "weird" but follows the rules, it's right. Formal English often sounds slightly unnatural to our modern ears, especially when it comes to things like "whom" or proper pronoun cases after "than" (e.g., "He is taller than I," not "He is taller than me").
The ACT English section is a game of patterns. Once you see the patterns, the "rules" stop being a list of chores and start being the cheat code to a higher score. Focus on the mechanics, keep your sentences lean, and don't let the commas push you around.