Idioms

Overview

Idioms are fixed expressions in English where the combination of words has a meaning that cannot be deduced from the individual words themselves. On the ACT English test, idiom questions assess whether students can recognize the conventional, accepted phrasing that native speakers use naturally. These questions do not test obscure sayings or colorful expressions like "raining cats and dogs"; instead, they focus on prepositional idioms and standard word pairings that appear in formal academic writing. Understanding ACT idioms is crucial because these questions have no logical rule to follow—the correct answer is simply "what sounds right" to educated English speakers, making them particularly challenging for non-native speakers and students who haven't been extensively exposed to standard written English.

The ACT English section includes idiom questions in approximately 10-15% of all grammar and usage items, making this a high-yield topic that can significantly impact your score. These questions typically appear as underlined portions where you must choose between different prepositions or word combinations. Unlike other grammar rules that follow logical patterns, idioms must be memorized through exposure and practice. The good news is that the ACT tests a relatively limited set of common idioms repeatedly, so focused study can yield substantial score improvements.

Idioms connect closely to other English concepts tested on the ACT, particularly word choice and style. While word choice questions focus on selecting the most precise vocabulary, idiom questions specifically test conventional phrings. Both require an ear for natural English expression. Additionally, idiom mastery supports your understanding of sentence structure and clarity, as incorrect idioms often create awkward or unclear sentences even when they are grammatically correct in other respects.

Learning Objectives

• [ ] Identify when Idioms is being tested on ACT English questions
• [ ] Explain the core rule or strategy behind Idioms and why they cannot be logically deduced
• [ ] Apply Idioms to ACT-style questions accurately by recognizing correct prepositional pairings
• [ ] Distinguish between idiom errors and other types of grammar or usage errors
• [ ] Memorize the 30-40 most commonly tested idiom patterns on the ACT
• [ ] Develop an "ear" for correct idiomatic expressions through pattern recognition
• [ ] Eliminate incorrect answer choices by identifying non-standard prepositional pairings

Prerequisites

• Basic parts of speech: Understanding prepositions, verbs, adjectives, and nouns is essential because idioms typically involve specific preposition choices following particular words
• Sentence structure fundamentals: Recognizing how phrases function within sentences helps identify where idioms appear and what they modify
• Reading comprehension skills: The ability to understand context helps determine which idiom makes sense in a given passage, even when multiple options might seem plausible

Why This Topic Matters

Idioms represent one of the most practical aspects of language mastery. In real-world communication, using incorrect idioms immediately signals to listeners or readers that the speaker is not fully fluent in English. Professional writing, academic papers, and business communications all require correct idiomatic usage to maintain credibility and clarity. When someone writes "interested about" instead of "interested in," or "different than" instead of "different from," educated readers notice these errors, which can undermine the writer's authority.

On the ACT English test, idiom questions appear with remarkable consistency. Approximately 2-3 questions per test (out of 75 total English questions) directly test idiomatic expressions. These questions typically appear in the Conventions of Standard English category, specifically under Knowledge of Language. The questions are distributed throughout the test passages and can appear in any content area—from humanities to natural sciences. Because idiom questions have only one correct answer with no logical rule to apply, they are either completely right or completely wrong, making them high-stakes items that reward preparation.

Common ways idioms appear on the ACT include: prepositional idioms following adjectives (concerned with, worried about), prepositional idioms following verbs (rely on, depend on), correlative expressions (not only...but also, between...and), and comparative constructions (different from, similar to). The test writers deliberately include answer choices with prepositions that might seem logical but are not conventionally accepted. Understanding these patterns allows students to quickly identify idiom questions and apply their memorized knowledge efficiently.

Core Concepts

What Makes an Idiom

An idiom in the context of ACT testing refers to a conventional phrase or expression where specific words must be used together in a fixed pattern. Unlike grammar rules that follow logical principles, idioms are established purely by convention—they are correct because educated English speakers have agreed they are correct over time. The ACT focuses specifically on prepositional idioms, where particular prepositions must follow certain verbs, adjectives, or nouns.

The key characteristic of idioms is their arbitrariness. There is no logical reason why we say "interested in" rather than "interested about" or "interested with"—it is simply the accepted form. This arbitrariness makes idioms challenging because students cannot reason their way to the correct answer; they must either know the idiom or recognize it from prior exposure.

Prepositional Idioms with Adjectives

Many ACT idiom questions test which preposition correctly follows an adjective. These combinations are fixed and must be memorized:

The ACT frequently tests these by offering answer choices with different prepositions. For example, a question might underline "different than" and offer "different from," "different to," and "different with" as alternatives. Only "different from" is correct in standard American English.

Prepositional Idioms with Verbs

Verbs also pair with specific prepositions to create idiomatic expressions. These verb-preposition combinations are among the most frequently tested on the ACT:

Note that some verbs can take different prepositions with different meanings. "Result in" means to cause or produce something, while "result from" means to be caused by something. The ACT may test whether students understand these subtle distinctions.

Correlative Idioms

Correlative idioms are two-part expressions where specific words must appear together. These are highly testable because the ACT can place the two parts far apart in a sentence, making it harder to recognize the pairing:

• not only...but also: She not only studied hard but also participated in study groups.
• either...or: Students can either submit the paper early or request an extension.
• neither...nor: The solution was neither practical nor affordable.
• between...and: The difference between success and failure often comes down to preparation.
• both...and: The program benefits both students and teachers.
• as...as: This method is as effective as the traditional approach.
• from...to: Temperatures range from 60 to 80 degrees.

The most common error with correlative idioms is mixing pairs, such as "not only...but" (missing "also") or "between...or" (should be "and"). The ACT tests whether students can identify when these pairs are incomplete or incorrectly matched.

Comparative and Equality Idioms

Expressions of comparison follow specific idiomatic patterns:

• different from (not "different than" in formal writing)
• similar to (not "similar as" or "similar with")
• the same as (not "the same like")
• prefer...to (not "prefer...over" or "prefer...than")
• regard as (not "regard to be")
• consider (takes no preposition: "consider it important," not "consider it as important")

These comparative idioms are particularly tricky because some alternatives might seem logical. For instance, "different than" is sometimes accepted in informal speech, but the ACT consistently prefers "different from" in formal written English.

Common Verb-Noun Idioms

Certain verbs pair with specific nouns in fixed expressions:

• make a decision (not "take a decision")
• do homework (not "make homework")
• take a test (not "make a test" or "do a test")
• pay attention (not "give attention" in this context)
• have an effect on (not "have an affect on")
• take advantage of (not "take the advantage of")

While these might seem obvious to native speakers, they represent arbitrary conventions that must be learned.

Concept Relationships

Idioms connect to other ACT English concepts in several important ways. First, idiom questions often overlap with word choice questions, as both test whether students can select the most appropriate expression. However, word choice focuses on precision and meaning, while idioms focus purely on conventional phrasing. A student might understand the meaning perfectly but still choose the wrong idiom because they select a logical but non-standard preposition.

Second, idioms relate to sentence structure because incorrect idioms can create awkward or unclear sentences. When a sentence uses "interested about" instead of "interested in," the sentence becomes harder to process, even though the grammar might be technically correct. This connection means that developing an ear for idioms simultaneously improves overall sentence clarity.

Third, idioms connect to style and tone because using correct idioms is a marker of formal, educated writing. The ACT English section tests formal written English, and correct idiomatic usage is a key component of that register. Students who master idioms are better equipped to handle style questions that ask them to maintain consistency in formality level.

The relationship map looks like this: Prepositional Knowledge → enables recognition of → Prepositional Idioms → which combine with → Verb/Adjective/Noun Patterns → to create → Standard Idiomatic Expressions → which support → Clear, Formal Writing → which is tested through → ACT Idiom Questions.

High-Yield Facts

⭐ The ACT tests approximately 30-40 common idioms repeatedly; memorizing these high-frequency expressions yields significant score improvements.

⭐ "Different from" is always correct on the ACT; "different than" is considered informal and will never be the right answer.

⭐ Prepositional idioms cannot be logically deduced—they must be memorized through exposure and practice.

⭐ When a question offers four different prepositions as answer choices, it is almost certainly testing an idiom.

⭐ Correlative expressions like "not only...but also" must include both parts; incomplete pairs are always incorrect.

• The verb "consider" never takes a preposition in formal writing; "consider it important" is correct, not "consider it as important."

• "Interested in" is correct; "interested about" and "interested with" are never standard.

• "Concerned with" and "concerned about" are both acceptable, but they have slightly different meanings (with = dealing with; about = worried about).

• "Rely on" and "depend on" are correct; "rely upon" and "depend upon" are also acceptable but less common.

• The expression "regard as" is correct; "regard to be" is incorrect.

• "Between...and" is the correct pairing; "between...or" is always wrong.

• "Prefer...to" is the formal construction; "prefer...over" is less formal and rarely correct on the ACT.

• "Capable of" is correct; "capable to" is incorrect.

• "Prohibit from" is correct; "prohibit to" is incorrect.

• "Subscribe to" (a magazine or idea) is correct; "subscribe in" is incorrect.

Common Misconceptions

Misconception: Idioms can be figured out logically by thinking about what makes sense.

Correction: Idioms are arbitrary conventions that cannot be deduced through logic. While "interested about" might seem logical (you're interested about a topic), the correct form is "interested in" purely by convention. Students must memorize common idioms rather than trying to reason them out.

Misconception: "Different than" is acceptable in formal writing because it's commonly used in speech.

Correction: While "different than" appears in informal speech and some regional dialects, the ACT consistently treats "different from" as the only correct form in formal written English. On test day, always choose "different from."

Misconception: If an idiom sounds right, it must be correct.

Correction: Students whose primary exposure to English comes from informal sources (social media, casual conversation) may have internalized non-standard idioms. What "sounds right" depends on what you've been exposed to. The ACT tests formal, educated written English, which may differ from casual speech patterns.

Misconception: All prepositions are interchangeable after a given word.

Correction: Prepositions are not interchangeable in idiomatic expressions. "Worried about" and "worried of" are not both correct—only "worried about" is standard. Each adjective or verb pairs with specific prepositions, and these pairings must be memorized.

Misconception: Correlative expressions like "not only...but also" can be shortened to "not only...but" without changing correctness.

Correction: Correlative expressions must include both parts to be complete and correct. "Not only...but" is incomplete; the full expression "not only...but also" is required in formal writing. The ACT will mark incomplete correlatives as incorrect.

Misconception: The verb "consider" needs a preposition like "as" to be complete.

Correction: The verb "consider" is unique in that it takes a direct object and a complement without any preposition. "I consider him intelligent" is correct; "I consider him as intelligent" is incorrect. This is one of the most commonly tested idioms on the ACT.

Worked Examples

Example 1: Prepositional Idiom with Adjective

Passage: "The researchers were interested about the effects of climate change on coastal ecosystems."

Question:

A. NO CHANGE

B. interested in

C. interested with

D. interested to

Step 1 - Identify the question type: The underlined portion contains an adjective ("interested") followed by a preposition, and all answer choices offer different prepositions. This is clearly testing a prepositional idiom.

Step 2 - Recall the correct idiom: The standard idiom is "interested in." This must be memorized—there's no logical way to deduce it.

Step 3 - Eliminate incorrect choices:

• Choice A ("interested about") is non-standard
• Choice C ("interested with") is non-standard
• Choice D ("interested to") is non-standard

Step 4 - Select the correct answer: Choice B is correct. The sentence should read: "The researchers were interested in the effects of climate change on coastal ecosystems."

Connection to learning objectives: This example demonstrates how to identify idiom questions (objective 1) by recognizing the pattern of multiple preposition choices, and how to apply memorized idiom knowledge (objective 3) to select the correct answer.

Example 2: Correlative Idiom

Passage: "The new policy benefits not only students but teachers as well."

Question:

A. NO CHANGE

B. not only students but also

C. not just students but

D. not only students and

Step 1 - Identify the question type: The underlined portion contains the first part of a correlative expression ("not only...but"). The question is testing whether the correlative pair is complete and correct.

Step 2 - Recall the correct correlative idiom: The standard correlative expression is "not only...but also." Both parts must be present.

Step 3 - Analyze each choice:

• Choice A is incomplete—it has "not only...but" without "also"
• Choice B correctly includes both parts: "not only...but also"
• Choice C uses "not just...but," which is less formal and incomplete
• Choice D uses "not only...and," which breaks the correlative pair

Step 4 - Select the correct answer: Choice B is correct. The sentence should read: "The new policy benefits not only students but also teachers."

Step 5 - Verify in context: Reading the complete sentence confirms that "not only...but also" creates a balanced, formal construction appropriate for the ACT.

Connection to learning objectives: This example shows how to identify correlative idiom questions (objective 1), explains why the correct form must include both parts of the pair (objective 2), and demonstrates the application process (objective 3).

Exam Strategy

When approaching idiom questions on the ACT English test, follow this systematic process:

Recognition triggers: Idiom questions typically present themselves in specific ways. Watch for answer choices that offer four different prepositions (in, on, with, about) or four different versions of correlative expressions. If you see this pattern, you're almost certainly dealing with an idiom question. Another trigger is when all answer choices seem grammatically correct but use different words—this suggests the question is testing conventional phrasing rather than grammar rules.

The "ear test" approach: For students who have extensive exposure to formal written English, the ear test can be effective. Read each answer choice aloud (silently, in your head) and listen for which one sounds most natural in formal writing. However, this strategy only works if your "ear" has been trained on standard written English, not informal speech. If you're unsure, rely on memorized idiom lists rather than intuition.

Process of elimination: Even if you don't immediately know the correct idiom, you can often eliminate clearly wrong answers. If you know "interested with" sounds completely wrong, eliminate it even if you're unsure whether the answer is "interested in" or "interested about." Narrowing to two choices significantly improves your odds.

Time management: Idiom questions should be among your fastest questions because they require no complex analysis—you either know the idiom or you don't. Spend no more than 20-30 seconds per idiom question. If you don't immediately recognize the correct answer, make your best guess and move on. Don't waste time trying to logic your way through an idiom question, as this approach rarely works.

Context clues: While idioms themselves are arbitrary, the surrounding context can sometimes help. If a sentence discusses differences between two things, you know you need "different from." If it discusses what someone is worried about, you need "worried about" not "worried of." Use context to confirm your idiom choice makes sense in meaning, even though the idiom itself is conventional.

Common trap patterns: The ACT frequently includes "almost correct" answers that use prepositions that seem logical but aren't standard. For example, "different than" is a common trap because it's used in informal speech. "Interested about" is another trap because "about" seems to make logical sense. Train yourself to recognize these common traps and automatically eliminate them.

Memory Techniques

The "IN" mnemonic: Many common adjectives pair with "in": Interested IN, Involved IN, Engaged IN, Successful IN. Remember "I'M IN" (Interested, Involved, Engaged, Successful are all IN).

The "OF" mnemonic: Several adjectives pair with "of": Capable OF, Aware OF, Fond OF, Jealous OF. Remember "CAFJ drinks OF" (Capable, Aware, Fond, Jealous all take OF).

Correlative pairs visualization: Picture correlative expressions as two hands that must clasp together—both parts are needed. "Not only" is one hand reaching out; "but also" is the other hand completing the clasp. If one hand is missing, the connection fails.

The "FROM" rule: When comparing or showing difference/distance, think "FROM": Different FROM, Distinguish FROM, Separate FROM, Apart FROM. The word "from" indicates origin or separation, which aligns with comparison concepts.

Verb-preposition stories: Create mini-stories to remember verb-preposition pairs. "I RELY ON my friend" (picture leaning on someone). "I DEPEND ON my alarm" (picture hanging from a clock). "I PARTICIPATE IN activities" (picture being inside a circle of activities).

The "consider" exception: Remember that "consider" is the rebel verb—it refuses to take a preposition. Picture "consider" as a stubborn character who says "I don't need any prepositions!" This helps you remember: "consider it important" NOT "consider it as important."

Flashcard grouping: Create flashcard groups by preposition. Put all "with" idioms on blue cards, all "in" idioms on green cards, all "of" idioms on yellow cards. The color coding helps your brain categorize and recall the patterns.

Summary

Idioms represent one of the most straightforward yet challenging topics on the ACT English test. Unlike grammar rules that follow logical patterns, idioms are conventional expressions that must be memorized through exposure and practice. The ACT focuses primarily on prepositional idioms—specific prepositions that must follow certain adjectives, verbs, and nouns—and correlative expressions that require both parts to be complete. Success on idiom questions depends on recognizing the question type (typically signaled by answer choices offering different prepositions) and applying memorized knowledge of the 30-40 most commonly tested idioms. Students cannot reason their way to correct answers on idiom questions; they must either know the standard expression or make an educated guess. The high-yield strategy involves memorizing the most frequently tested idioms, particularly "different from," "interested in," "not only...but also," and the unique behavior of "consider" (which takes no preposition). With focused study of common idiom patterns and regular practice, students can quickly master this topic and secure easy points on test day.

Key Takeaways

• Idioms are conventional expressions that cannot be logically deduced—they must be memorized through exposure to standard written English
• The ACT tests approximately 30-40 common idioms repeatedly, making focused memorization a high-yield study strategy
• Prepositional idioms (adjective/verb + preposition) are the most frequently tested idiom type on the ACT
• "Different from" is always correct on the ACT; "different than" is never the right answer in formal writing
• Correlative expressions like "not only...but also" must include both parts to be correct
• When answer choices offer four different prepositions, the question is almost certainly testing an idiom
• The verb "consider" never takes a preposition in formal writing—a unique exception that appears frequently on the ACT

Related Topics

Word Choice and Diction: While idioms test conventional phrasing, word choice questions test precision and appropriateness of vocabulary. Mastering idioms provides a foundation for understanding how context determines the best word or phrase selection.

Sentence Structure and Clarity: Correct idiomatic usage contributes to clear, natural-sounding sentences. Understanding idioms helps students recognize when sentences are awkward or unclear due to non-standard phrasing.

Prepositions and Prepositional Phrases: A deeper study of how prepositions function in sentences enhances idiom mastery, as most ACT idioms involve prepositional choices.

Style and Tone: Idioms are markers of formal, educated writing. Students who master idioms are better prepared to handle questions about maintaining consistent formality and appropriate register throughout a passage.

Practice CTA

Now that you understand the core concepts and strategies for ACT idioms, it's time to put your knowledge into practice! Work through the practice questions to test your ability to identify and correct idiomatic expressions. Use the flashcards to memorize the most commonly tested idiom patterns—repetition is key to internalizing these conventional expressions. Remember, idiom mastery is one of the fastest ways to improve your ACT English score because these questions have definitive right answers that you can learn to recognize instantly. With focused practice, you'll develop the "ear" for correct idioms that will serve you well on test day and in your future academic writing. You've got this!