English can be tricky, and the ACT takes advantage of that. The test checks whether you can choose the correct word when two options sound the same or look similar but mean different things.

Below is a short list of word pairs (and trios) the ACT often uses to create confusion. They’re listed in roughly the order you’re most likely to see them.

Its/It’s

This one is common enough that we devoted a chapter to it. Check out It’s and its.

Here’s a quick summary:

• It’s = it is
• Its = possessive form of “it.”
• Its’ = this does not exist in the English language. You’ll see it on the ACT though as “grammatically incorrect.”

EXAMPLE

It’s = it is

It’s cold outside!

Its = possessive form of “it.”

The honey badger is protective of its food.

Who/Whom

The difference between who/whom is the same as the difference between he/him or she/her.

• Use who when the word is a subject (like he or she).
• Use whom when the word is an object (like him or her).

A quick way to check is to replace who/whom with he/him (or she/her) and see which one works grammatically.

Example

Who/whom said that and to who/whom were they speaking?

Look at the first blank. Try substituting he/him:

• “He said that” works.
• “Him said that” doesn’t.

So the correct choice is who.

Exercise

I’m sorry, but you spoke to who on the phone?

A. NO CHANGE
B. to whom, on the phone?
C. to who, on the phone?
D. to whom on the phone?

The commas are there to distract you. There’s no rule that requires a comma here, so eliminate choices B and C.

Now decide between A and D by substituting her/she:

• “spoke to her on the phone” works.
• “spoke to she on the phone” doesn’t.

So the correct answer is D.

Remember:

• Who = he or she = Someone doing something
• Whom = him or her = Something happening towards, at, or to someone

Affect/Effect

This pair confuses a lot of people, but the core rule is straightforward:

• Affect = usually, but not always, a verb
• Effect = usually, but not always, a noun

If you want a refresher on nouns and verbs, see the chapter on Parts of speech.

Examples

While the words of the speech were stirring, they didn’t affect me as much as the delivery.

Here, affect is the verb describing what “they” did.

While the words of the speech were stirring, they didn’t have as great an effect on me as her delivery.

Here, effect is a noun (the thing they “had”).

Their/They’re/There

These are some of the most common errors on the ACT (and in everyday writing). They sound the same, but they have different meanings.

• Their = Possessive form of the word “they.” When “they” own something, it’s “their” books.
• They’re = Shortened form of “they are.” That’s it. It really is that simple.
• There = In technical terms, this is called a demonstrative pronoun. All that really means is that we use it to refer to a place. You know, over “there.” It is also used in metaphorical ways, like, “There is the real problem” or “There are many good ideas in this discussion.”

Example

This isn’t exactly like an ACT question, but it gives you efficient practice with all three.

The students were told that there are things there young minds need to know before there pushed off into the “real world.”

For each of the three underlined words above, pick the correct choice:

A. NO CHANGE
B. their
C. they’re

The first one is A: NO CHANGE. Here, “there” is used in the broad, introductory way: “There are things…”

Number two is B: their because the sentence needs a possessive word. The young minds belong to the students.

Number three is C: they’re. If you substitute “they are,” the sentence makes sense: “…before they are pushed off into the ‘real world.’”

Then/Than

These two words are only one letter apart, so they’re easy to miss. Keep the meanings separate:

• Then = a moment in time
• Than = used to compare

Example

I finished my work, and then I went for a walk in the park.

Here, “then” refers to time: after finishing work, the speaker went for a walk.

Margaret is taller than her younger sister.

Here, “than” is used for a comparison.