163 ACT Vocab Words You Must Know

Many students are aware that you need a good vocabulary to do well on the ACT, but they're often not sure just how their vocabulary will be tested. Gone are the days where you needed to learn the definitions of dozens of obscure words, but a good vocabulary is still key to excelling on the ACT. To help you out, we've compiled a list of 163 key ACT vocabulary words to know. We also explain how vocab is tested on the ACT, the types of questions you'll see, and the best way to study ACT vocab words.

How Does the ACT Test Vocabulary?

Standardized tests in general have shifted away from emphasizing vocabulary, and the ACT is part of that trend. Whereas before it was common to have questions that directly asked you about the definition of a word, there is now much more of a focus on understanding words in context, rather than being able to rattle off dozens of word definitions strictly from memory.

However, a strong vocabulary will absolutely help you on the ACT, especially if you're aiming for a high or perfect score. Even if fewer questions ask directly about word definitions, an expansive vocabulary will help you read through passages more quickly and have a more solid understanding of the topics they're discussing.

ACT vocabulary questions are now primarily focused on testing your ability to understand and define words in context. You may see them in either the Reading or English sections.

Some of the words you'll be asked about may be unusual, but most or all of them should be known to you. You'll no longer be expected to know the definitions of obscure words that you rarely hear in normal life. Question 19, below, is an example of an ACT English question you might see. This example comes from an official ACT practice test.

To answer question 19 correctly, you'd need to know the definitions of cumbersome, thorny, strenuous, and gawky. You've likely heard or read each of these words, although you may not be rock solid on every definition. You also need to get context from the passage to answer the question. If you read through the entire passage, you'll learn that the Navajo code was much easier to use than previous codes, so you know the best answer for question 19 will be a word that contrasts with "simple" or "easy." Cumbersome, defined as "unwieldy" or "burdensome" is the best choice, so the correct answer is A.

Here's the type of vocab question you might see in ACT Reading:

Humor is a word you know, but all four answer choices could be correct depending on the context. You'd need to read the passage and understand which option fits the context best to answer the question.

As you can see, the vocab words tested on the ACT don't often go beyond a medium-level difficulty, but you still need to have a solid vocabulary and understand how to define words in specific contexts.

163 ACT Vocabulary Words to Know Before Test Day

Below is a table of the 163 top ACT vocabulary words to study and know. For each word, we include the definition and an example sentence that contains the word so you have more context for it.

To compile this list, we read through every publicly available official ACT practice exam and looked at both the Reading and Writing sections (and not just the questions but the answer choices and passages, too). We also used our own knowledge of the types of words you can expect to see most often on standardized tests. 

Though you don’t need to memorize every word in this chart, familiarizing yourself with most of them will help you better identify the tones of passages and make you more efficient at interpreting and answering questions correctly on the ACT.

How Should You Study ACT Vocabulary Words: The Waterfall Method

Anyone hoping to get a high score on the ACT should study using official ACT practice tests. Take these tests timed, and in one sitting, to get the most accurate estimate of how you'd score on the actual ACT. As you go through practice tests and additional practice problems, take note of any words they include that you are unsure of. Add these to your ACT vocab words to study. Similarly, if there are words from the above list that you are confident about, you don't need to spend additional time studying them.

When you have your set of ACT vocabulary words you want to study, we recommend turning them into flashcards. Flashcards are a great way to test yourself on vocab. They don't take long to make, and you can quiz yourself on them again and again until you know all the words. We recommend creating physical flashcards (as opposed to online flashcards) because then you can use our preferred flashcard study method: The Waterfall Method. With this method, you'll get to see all the words in your ACT vocab list, going over the most challenging words more often than the ones you already know or sort of know.

Once you have your list of ACT vocabulary words and your flashcards made, here's how to use the waterfall method:

Once you’ve made your flashcards, split them up into decks (you can put whatever words you want in these decks) of about 30-50 cards each. Choose one deck to be your Starting Stack. 

Go through your Starting Stack, looking at each and every card. For the words you know, put them in a Know It pile. For the words you don’t know, put them in a separate Struggled pile as so:

Now, pick up your Struggled pile and go through each card in it (leave your Know It pile where it is). Put the cards you know in a second Know It pile and the ones you don’t know in a Struggled pile.

You should now have two Know It piles and one Struggled pile:

Repeat this process of picking up your Struggled pile and going through each card until you’re left with about one to five cards in your Struggled pile:

By now you should know most, if not all, cards in your deck. But it isn’t enough to just go through them once—you also have to work back up your “waterfall” of cards. 

To do this, combine your Struggled pile with your last Know It pile (the pile closest to the Struggled pile). This will be your Working pile. Go through all the cards in this pile. If there are any words you forgot, go through the entire pile of ACT vocab flashcards again and again until you've learned all the definitions in it.

Continue this pattern by combining your current Working pile with the next Know It pile. Go through all these cards until you know each one.

At the end, you should have made your way all the back to your original Starting Stack. You now know all the ACT words and their meanings in your deck! Repeat this waterfall method with the other decks you make so that you can learn even more critical ACT test vocabulary.

What's Next?

Practice tests are one of the best ways to prepare for the ACT. We have links to every free and official ACT available, so you can get started with your studying!

Not sure when to take the ACT? Get a complete study plan for the ACT to figure out the best date for you.

Taken the ACT already but unhappy with your score? Use our guide to decide whether you should retake the ACT.