ACT English: Mastering the Conventions of Standard English

Sentence Structure and Formation

A sentence is a complete unit of thought. On the ACT, “Conventions of Standard English” questions often test whether your sentence is built from the right parts in the right shape. The foundation is the independent clause—a group of words with a subject and a verb that can stand alone as a complete sentence. Many errors happen when writers accidentally leave out a necessary piece (creating a fragment) or cram too much together without the right connector (creating a run-on).

To build a clear sentence, first identify the core: who/what (subject) does what (verb). Then add details (objects, phrases, clauses) without breaking the grammar. Two common “good” sentence patterns are:

• One independent clause: “The researcher recorded the results.”
• An independent clause plus extra information added correctly: “The researcher recorded the results after the trial ended.”

Show it in action:

• Core + modifier phrase: “The students, tired after practice, finished the homework.” The core is “students finished.” The inserted phrase adds description but doesn’t change the core.
• Core + dependent clause: “Because the data were incomplete, the conclusion changed.” The dependent clause (“Because…”) needs the independent clause to complete the thought.

A key habit for ACT editing is to locate the main verb and ensure the subject matches it and the sentence has a complete main-clause backbone.

Exam Focus

• Typical question patterns:
  • Choosing between punctuation/connector options to make a sentence complete.
  • Identifying whether an underlined portion creates a complete sentence.
  • Fixing “awkward” structures by restoring a clear subject–verb core.
• Common mistakes:
  • Treating long sentences as automatically wrong (length isn’t the issue; structure is).
  • Missing the real subject because of interrupting phrases.
  • Adding details that accidentally remove the main clause.

Run-On Sentences and Comma Splices

A run-on sentence happens when two independent clauses are joined without an appropriate connector or punctuation. A comma splice is a specific run-on: two independent clauses joined by only a comma. These are heavily tested because they’re easy to spot and easy to fix—if you know your options.

Why it matters: run-ons confuse readers by blurring where one complete thought ends and another begins. On the ACT, the “right” answer usually depends on recognizing independent clauses and choosing a legal way to join them.

How to fix two independent clauses:

1. Period: Make two sentences.
2. Semicolon: Join closely related independent clauses.
3. Comma + coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so).
4. Subordination: Make one clause dependent (using because, although, when, etc.).

Show it in action:

• Comma splice: “The storm ended, the streets were still flooded.”
  • Fix (semicolon): “The storm ended; the streets were still flooded.”
  • Fix (comma + conjunction): “The storm ended, but the streets were still flooded.”
• Run-on (no punctuation): “I wanted to go I had no ride.”
  • Fix (subordination): “Although I wanted to go, I had no ride.”

A common trap: if one part is not an independent clause, you don’t need semicolons or conjunctions—you may just need a comma (or no punctuation).

Exam Focus

• Typical question patterns:
  • Selecting punctuation to correctly join two complete sentences.
  • Deciding whether to use a semicolon, period, or comma + conjunction.
  • Converting one clause to dependent to improve clarity.
• Common mistakes:
  • Using a comma alone between two complete sentences.
  • Using a semicolon when one side isn’t an independent clause.
  • Adding a conjunction without the needed comma (or adding a comma where it doesn’t belong).

Sentence Fragments

A sentence fragment is a group of words punctuated like a sentence but missing a key element—usually a main verb, a subject, or a complete independent clause. Fragments often appear when writers start with a dependent clause or a phrase and forget to attach it to a full sentence.

Why it matters: the ACT tests whether each sentence expresses a complete thought. Fragments can sound “stylistic” in informal writing, but ACT English expects standard formal conventions.

Common fragment types and how they work:

• Dependent clause fragment: starts with because, although, when, since, if, etc. These words “promise” an explanation, contrast, or condition, but they can’t finish the thought alone.
• Phrase fragment: a prepositional phrase (“In the morning.”) or participial phrase (“Running down the street.”) without a main clause.
• Missing verb fragment: the sentence has a subject but no finite verb.

Show it in action:

• Fragment: “Because the paint was wet.”
  • Fix: “Because the paint was wet, we left the door open.”
• Fragment: “A solution to the problem.”
  • Fix: “A solution to the problem emerged during the meeting.”

Be careful: sometimes the ACT uses fragments in dialogue or for effect, but in the Conventions section, you’re usually expected to choose the grammatically complete option unless the context clearly supports a stylistic fragment.

Exam Focus

• Typical question patterns:
  • Choosing between a dependent-clause-only option and one that attaches it to an independent clause.
  • Fixing an underlined portion that removes the only main verb.
  • Combining a fragment with a nearby sentence.
• Common mistakes:
  • Thinking any group of words with a verb is a sentence (it must be independent).
  • Adding a comma to “fix” a fragment (punctuation can’t create a main clause).
  • Keeping a dependent clause alone because it “sounds dramatic.”

Parallel Structure

Parallel structure means expressing matching ideas in the same grammatical form. If two or more items play the same role in a sentence, they should “look” the same: nouns with nouns, -ing verbs with -ing verbs, clauses with clauses. Parallelism matters because it makes sentences easier to read and keeps the logic clean.

The ACT likes parallelism because it’s a precision skill: you check the pattern, then make the items match. Parallel structure often appears in lists, comparisons, paired constructions, and correlative conjunctions.

Common parallel “signals”:

• Lists: “She likes hiking, swimming, and biking.”
• Paired/conjoined ideas: “He was not only tired but also hungry.”
• Comparisons: “The new system is faster than the old one.” (Compare system to system, not system to using it.)

Show it in action:

• Faulty: “The job requires attention to detail, writing clearly, and you must be punctual.”
  • Parallel fix: “The job requires attention to detail, clear writing, and punctuality.”
• Correlative fix: “She not only designed the logo but also wrote the slogan.” (verb + verb)

A frequent error is mixing forms after “and/or” because the sentence is long; your job is to align the grammar of each item in the series.

Exam Focus

• Typical question patterns:
  • Fixing a list where one item doesn’t match the others.
  • Adjusting “not only…but also,” “either…or,” “both…and” structures.
  • Repairing comparisons that don’t compare the same kinds of things.
• Common mistakes:
  • Changing the wrong list item (usually you match the odd one to the established pattern).
  • Forgetting that entire clauses can be parallel, not just words.
  • Creating new agreement errors while trying to fix parallelism.

Coordination and Subordination

When you connect ideas, you’re choosing their relationship. Coordination links ideas of equal importance; subordination makes one idea dependent on another. The ACT tests this because it affects both grammar (what punctuation is legal) and meaning (what the sentence emphasizes).

Coordinating conjunctions (FANBOYS) join two independent clauses when paired with a comma: “I wanted to leave, but the bus was late.” Coordination is useful when both ideas deserve equal weight.

Subordinating conjunctions (because, although, when, since, if, while, etc.) create a dependent clause: “Because the bus was late, I stayed.” Subordination signals that one idea explains, contrasts with, or depends on the other.

Show it in action:

• Coordination: “The experiment failed, and the team revised the method.” (two main events)
• Subordination: “Although the experiment failed, the team revised the method.” (failure is background/contrast)

A common ACT decision is whether the sentence should show cause, contrast, or time. The “right” connector is the one that matches the logic of the passage, not just one that’s grammatically possible.

Exam Focus

• Typical question patterns:
  • Choosing between conjunctions like “because/although/when” to match meaning.
  • Fixing run-ons by adding a conjunction or changing punctuation.
  • Deciding whether to keep two ideas equal (and/but/so) or make one dependent.
• Common mistakes:
  • Using “however” like a conjunction (it needs different punctuation; it’s a transitional word).
  • Using a subordinating conjunction but leaving the clause alone (creating a fragment).
  • Picking a connector that changes the intended meaning (cause vs. contrast).

Commas, Semicolons, and Colons

These punctuation marks signal relationships between ideas. The ACT often rewards a simple rule: punctuation is not “style only”—it encodes grammar.

A comma has several major jobs:

• Separate items in a list.
• After introductory elements: “After the meeting, we left.”
• Set off nonessential (nonrestrictive) information.
• Before a coordinating conjunction joining two independent clauses.

A semicolon joins two independent clauses without a conjunction: “The lights flickered; the power returned.” It can also separate complex list items when those items contain commas.

A colon introduces something that explains or specifies what came before. Crucially, what comes before a colon must be able to stand as a complete sentence. Think of a colon as saying, “Here it is.”

Show it in action:

• Comma after intro: “In the early 1900s, the city expanded rapidly.”
• Semicolon vs comma: “The city expanded rapidly; it also modernized its transit.” (two independent clauses)
• Colon for explanation: “She had one goal: to finish the marathon.” (complete clause before the colon)

Common pitfalls include using a colon after a fragment (“Such as:” is especially risky) and using semicolons where one side isn’t a full independent clause.

Exam Focus

• Typical question patterns:
  • Choosing the correct punctuation between two clauses (comma, semicolon, period).
  • Deciding whether a colon is allowed based on whether the left side is a complete sentence.
  • Testing commas with introductory phrases and nonessential clauses.
• Common mistakes:
  • Using a semicolon with a dependent clause.
  • Putting a colon after “including/such as” when the left side isn’t complete.
  • Over-comma-ing: inserting commas between subject and verb or verb and object.

Apostrophes and Possessives

An apostrophe mainly does two jobs: show possession and form certain contractions. On the ACT, apostrophe questions often test whether you can distinguish possession from plural and handle tricky pronouns.

For possession:

• Singular noun: add ’s (“the teacher’s desk”).
• Plural noun ending in s: add ’ (“the teachers’ lounge”).
• Plural noun not ending in s: add ’s (“the children’s books”).

For contractions: “it’s” = “it is” or “it has.” The possessive pronoun “its” has no apostrophe.

Pronoun possessives never use apostrophes: its, your, their, whose. This is a common ACT trap because “who’s/whose” and “it’s/its” look similar.

Show it in action:

• Possessive vs plural: “The dogs’ bowls were empty.” (many dogs) vs “The dog’s bowl was empty.” (one dog)
• It’s/its test: If you can replace it with “it is,” use “it’s.” “The company increased its profits.” (“it is profits” makes no sense, so no apostrophe.)

Exam Focus

• Typical question patterns:
  • Choosing between “its/it’s,” “who’s/whose,” “their/there/they’re.”
  • Fixing possessives in noun phrases (“students projects” vs “students’ projects”).
  • Avoiding apostrophes for simple plurals.
• Common mistakes:
  • Writing “it’s” for possession.
  • Adding apostrophes to plural nouns (“apple’s” when you mean “apples”).
  • Misplacing the apostrophe in plural possessives (“dogs’s”).

Dashes and Parentheses

Dashes and parentheses are tools for inserting extra information. They’re tested because they must be used consistently and they interact with commas.

An em dash (—) can mark a strong break or insert an interruption. If you use a dash to set off an aside, you typically need two dashes (one to open, one to close) unless the dash ends the sentence.

Parentheses ( ) also insert extra information, but they make the aside feel more separate—like a whisper. Parenthetical information is usually less central than dash-set information.

A key rule: don’t mix punctuation styles for the same insertion. If you start the aside with a dash, don’t end it with a comma.

Show it in action:

• Dashes: “The final ingredient—the one we almost forgot—changed the flavor completely.”
• Parentheses: “The final ingredient (one we almost forgot) changed the flavor completely.”

Also watch capitalization and punctuation around parentheses: if the parenthetical is part of the sentence, it usually doesn’t take its own end punctuation.

Exam Focus

• Typical question patterns:
  • Choosing between commas, dashes, and parentheses to set off nonessential information.
  • Fixing mismatched punctuation (dash opened but comma closed).
  • Deciding whether the inserted phrase is essential (no punctuation) or nonessential (punctuation).
• Common mistakes:
  • Using only one dash in the middle of a sentence.
  • Double-punctuating (comma plus dash) without a clear reason.
  • Using parentheses where the sentence then becomes ungrammatical without the aside.

Subject-Verb Agreement

Subject-verb agreement means a singular subject takes a singular verb, and a plural subject takes a plural verb. The ACT tests agreement because distractions (phrases between subject and verb, tricky nouns, or inverted word order) can hide the true subject.

How it works: find the subject by asking “Who/what is doing the verb?” Then ignore interrupting phrases.

Common tricky cases:

• Prepositional phrases don’t change the subject: “The list of items is long.” (“list” is singular)
• Collective nouns (team, committee, family) are usually treated as singular in standard test English: “The team wins.”
• Either/neither are typically singular: “Neither of the answers is correct.”

Show it in action:

• “The bouquet of roses smells wonderful.” Not “smell”—the subject is “bouquet.”
• “There are many reasons.” In “there is/there are” constructions, the verb agrees with what follows.

A frequent ACT trap is choosing a verb that agrees with a nearby noun instead of the actual subject.

Exam Focus

• Typical question patterns:
  • Picking the correct verb form when a phrase sits between subject and verb.
  • Agreement in “there is/there are” and questions (“What are the causes?”).
  • Agreement with indefinite pronouns (each, everyone, neither).
• Common mistakes:
  • Agreeing with the closest noun (“roses smell” instead of “bouquet smells”).
  • Forgetting that “each” pushes singular.
  • Treating compound subjects as always plural (they depend on the connector and meaning).

Pronoun-Antecedent Agreement

A pronoun replaces a noun, and the antecedent is the noun the pronoun refers to. Pronoun-antecedent agreement means the pronoun must match the antecedent in number (singular/plural) and often in person (first/second/third).

Why it matters: disagreement creates confusion about who is being discussed. On the ACT, these questions often appear in sentences with indefinite pronouns or singular nouns that “feel” plural.

Key patterns:

• Singular antecedents need singular pronouns: “Each student must bring his or her calculator.” (Many modern contexts use singular “they” in real life, but standardized tests often prefer strict agreement.)
• Plural antecedents need plural pronouns: “All students must bring their calculators.”

Show it in action:

• Faulty: “Every runner tied their shoes.”
  • Fix by making plural antecedent: “All runners tied their shoes.”
  • Or keep singular pronoun: “Every runner tied his or her shoes.”

On the ACT, the cleanest fix is often to make the antecedent plural so “they/their” becomes clearly correct.

Exam Focus

• Typical question patterns:
  • Fixing “each/everyone/someone” paired with “they/their.”
  • Choosing between “his or her,” “their,” and rewriting to plural.
  • Ensuring pronouns match compound antecedents.
• Common mistakes:
  • Letting “they” refer to a clearly singular noun in formal test context.
  • Switching person mid-sentence (“one…you”).
  • Creating ambiguity when multiple nouns could be the antecedent.

Pronoun Case and Reference

Pronoun case is the form a pronoun takes depending on its job in the sentence. The main cases tested are:

• Subjective (subject): I, he, she, we, they
• Objective (object): me, him, her, us, them
• Possessive: my/mine, his, her/hers, our/ours, their/theirs

Why it matters: case errors can make sentences sound wrong and can change meaning. The ACT often tests this in compound structures (“between you and I”) and in comparisons.

How to choose the case: strip the sentence down.

• “Between you and I” → “between I” sounds wrong; it should be “between you and me.”
• “She is taller than him” vs “than he (is)”—both appear in real usage, but ACT questions usually push you toward the grammatically consistent form based on what’s implied. Many test items prefer “than he” when the verb is understood (“than he is”).

Pronoun reference means the pronoun clearly points to one specific antecedent. Vague “this,” “that,” or “which” can cause confusion if they refer to an entire idea without naming it.

Show it in action:

• Case: “My brother and I went.” (subject) vs “The coach called my brother and me.” (object)
• Reference: Vague: “The team lost the map, which was frustrating.” Clearer: “The team lost the map, a mistake that was frustrating.”

Exam Focus

• Typical question patterns:
  • Choosing “I/me,” “who/whom,” “they/them” based on sentence role.
  • Fixing “between you and I” and similar preposition + pronoun structures.
  • Revising vague “this/that/which” so the reference is clear.
• Common mistakes:
  • Picking “I” because it sounds formal (case depends on function, not formality).
  • Misidentifying the antecedent when multiple nouns appear.
  • Leaving a pronoun with no clear noun to refer to.

Verb Tense and Tense Consistency

Verb tense tells when an action happens (past, present, future). Tense consistency means you don’t shift tenses without a reason. The ACT tests tense because shifts can be subtle in a passage—especially when a narrative is mostly past tense, but a sentence accidentally jumps to present.

How it works: determine the passage’s time frame. Then check each verb against that “timeline.” Tense can change legitimately when the time changes (flashbacks, general truths, or ongoing effects), but random switching is usually wrong.

Common situations:

• Narrative past: Most events described as completed.
• Present general truth: Facts that remain true: “Water boils at…”
• Perfect tenses (has/have/had + past participle) show actions completed relative to another time.

Show it in action:

• Inconsistent: “Yesterday we walked to the store and buy snacks.”
  • Fix: “Yesterday we walked to the store and bought snacks.”
• Logical shift: “She studied for weeks, and now she feels ready.” (past effort, present feeling)

Be careful with “would” and “could” in narratives: they often indicate habitual past or “future in the past,” and they must fit the context.

Exam Focus

• Typical question patterns:
  • Selecting the verb tense that matches surrounding sentences.
  • Fixing a single underlined verb that causes an unnecessary tense shift.
  • Choosing between simple past and past perfect when sequencing matters.
• Common mistakes:
  • Changing tense because of one signal word without checking the larger passage time frame.
  • Overusing past perfect (“had walked”) when simple past is enough.
  • Missing that dialogue or general facts may legitimately use present tense.

Adjective and Adverb Usage

An adjective describes a noun (“a careful driver”). An adverb describes a verb, adjective, or another adverb (“drives carefully,” “truly helpful,” “very quickly”). The ACT tests this because certain words are commonly confused, and because some linking verbs take adjectives (not adverbs).

Why it matters: choosing the wrong form can change meaning or create a grammatically incorrect structure. A major concept is the difference between action verbs and linking verbs. Linking verbs (often forms of “be,” plus verbs like “seem,” “become,” “feel,” “appear”) connect the subject to a description. After a linking verb, you generally want an adjective.

Show it in action:

• Action verb: “She sings beautifully.” (adverb modifies “sings”)
• Linking verb: “She feels bad about it.” (adjective describes “she,” not the feeling action)

Common confusing pairs include good/well: “good” is usually an adjective; “well” is usually an adverb (though “well” can be an adjective meaning healthy: “I am well”).

Exam Focus

• Typical question patterns:
  • Choosing “good/well,” “real/really,” “bad/badly.”
  • Identifying whether a verb is linking (needs adjective) or action (often needs adverb).
  • Fixing comparative/superlative forms (“more better” etc.).
• Common mistakes:
  • Using an adverb after a linking verb (“feel badly” when meaning “feel bad”).
  • Assuming “well” always means healthy (often it’s an adverb).
  • Mixing up what the word is modifying (noun vs verb).

Modifier Placement

A modifier is a word or phrase that describes something else. Placement matters because modifiers are read as describing the nearest logical target. The ACT tests modifiers because misplacement creates unintended (sometimes funny) meanings—and because the fix is usually structural and clear.

Two important error types:

• Misplaced modifier: the modifier is too far from what it modifies.
• Dangling modifier: the sentence starts with a modifying phrase, but the subject that follows can’t logically perform the action described.

How to fix: put the modifier next to the word it describes, and ensure the sentence’s subject matches the modifier’s implied subject.

Show it in action:

• Misplaced: “She served sandwiches to the children on paper plates.” (Are the children on plates?)
  • Fix: “She served the children sandwiches on paper plates.”
• Dangling: “Walking to the library, the rain soaked my jacket.” (Rain wasn’t walking.)
  • Fix: “Walking to the library, I got my jacket soaked by the rain.”

Modifiers are also tied to punctuation: setting off a phrase with commas can make it nonessential, which changes meaning.

Exam Focus

• Typical question patterns:
  • Revising an introductory phrase so it correctly modifies the subject.
  • Moving an underlined phrase to eliminate ambiguity.
  • Choosing punctuation that correctly sets off a nonessential modifier.
• Common mistakes:
  • Keeping the original subject even though it can’t logically “do” the modifier.
  • Fixing grammar but creating a new unclear meaning.
  • Ignoring that the shortest answer is often best only if it’s logically correct.

Idiomatic Expressions and Preposition Usage

Idioms are standard, conventional word pairings in English (“interested in,” “capable of,” “different from/than”). The ACT tests idioms because they are part of “standard usage,” and the test expects the most widely accepted formal option.

Prepositions (in, on, at, by, for, to, with, of, from, etc.) often appear in idioms, and the “right” choice usually can’t be derived from logic—you learn it by familiarity. Still, you can approach these questions systematically.

How to handle idiom questions:

1. Identify that it’s an idiom issue: the sentence is grammatically fine, but one word choice sounds off.
2. Prefer the choice that matches standard phrasing and keeps the sentence concise.
3. Avoid unnecessary prepositions or wordy constructions.

Show it in action:

• “responsible for” (not typically “responsible of”)
• “between X and Y” (between is for two; “among” is often used for three or more in formal rules, though real usage varies)
• “prefer X to Y” is a common tested pattern.

Also watch for verb + preposition pairs: “concentrate on,” “contribute to,” “comply with.” If the ACT offers multiple options, the correct one is usually the conventional pairing.

Exam Focus

• Typical question patterns:
  • Choosing the correct preposition in a fixed expression (“focus on,” “different from,” “compared with/to”).
  • Eliminating unnecessary words to match standard idiom and concision.
  • Fixing “between/among,” “like/as” in comparisons.
• Common mistakes:
  • Picking what sounds logical rather than what is idiomatic.
  • Adding extra prepositions (“discuss about”)—“discuss” usually doesn’t take “about.”
  • Changing an idiom in a way that introduces wordiness or ambiguity.