ACT grammar rules with practice questions

To prepare for ACT grammar questions, learn how clauses fit together, how words agree and how punctuation marks those relationships. Then practice explaining your choices. This guide covers eight selected rules with original exercises; it is a starting set of lessons, not every skill in ACT English.

What grammar covers on ACT English

ACT places grammar, punctuation and usage in Conventions of Standard English, approximately 38–43% of the section. The remaining categories cover writing decisions such as organization, purpose, precision and concision. ACT's English description explains these distinctions. Learning grammar alone will leave part of your preparation unfinished.

On the test, you edit passages. For the short drills below, choose the best replacement for the underlined text while leaving the rest unchanged. These are original teaching exercises, not official ACT questions or a full practice section. Work through all eight before reading the answer key. When you move to a timed section, use the ACT format and timing guide to plan the rehearsal.

Eight rules to practice

ACT's English standards include the skills below. Their order here is a teaching sequence, not a ranking of how often they appear.

1. Identify clauses before joining them

An independent clause has a subject and verb and can stand as a complete sentence. Adding a word such as “although” can make it dependent: “The archive closed” is complete; “Although the archive closed” leaves a thought unfinished. Purdue's clause guide explains the distinction.

Two independent clauses need a valid connection. A period, a semicolon or a comma with a coordinating conjunction can work. A comma alone creates a comma splice. For example: “The archive closed, but the online catalog remained available.” Read both clauses before choosing the mark.

2. Put a colon after a complete clause

A colon can introduce a list or explanation after a complete clause: “The kit contained two instruments: a compass and a thermometer.” Do not put it directly after “contained,” separating the verb from its objects. Purdue's punctuation overview distinguishes colons from semicolons. A semicolon can join independent clauses; it can also separate items in a complex list that already contains commas.

3. Use paired commas for an interruption

Extra information in the middle of a sentence needs punctuation on both sides. In “The Cedar Observatory, which opened last spring, welcomes visitors,” the relative clause adds information about an already identified observatory. If a phrase instead identifies which object you mean, setting it off can change the meaning. Purdue's essential and nonessential examples show the difference. Test what the phrase does before removing it.

4. Match the verb to its subject

In “The collection of photographs fills two drawers,” the subject is “collection.” The nearby plural “photographs” does not make the verb plural. Temporarily set aside “of photographs” and check “collection fills.” Purdue's agreement guidance addresses intervening phrases. Finding the subject is more reliable than matching the verb to the closest noun.

5. Distinguish possession from a plural or contraction

One gardener's notebook belongs to one gardener. Several gardeners' notebooks belong to several gardeners. A plural noun already ending in s takes the apostrophe after that s; a singular noun such as “gardener” takes apostrophe-s. Possessive “its” has no apostrophe. Expand “it's” to “it is” or “it has” to test whether a contraction fits. Purdue's apostrophe guide explains possessives and contractions.

6. Keep parallel items in the same form

“The workshop covers sketching, carving and polishing” gives all three activities the same grammatical form. Replacing “polishing” with “to polish” breaks the pattern. For a list or paired construction, compare the units being joined. Purdue's parallel-structure examples show that the pattern can involve words, phrases or clauses. You need to identify the units before matching them.

7. Give an introductory modifier the right subject

“Carrying a stack of folders, Maya entered the office” makes Maya the person carrying them. “Carrying a stack of folders, the office door swung open” assigns that action to the door. When an opening participial phrase omits its actor, check the subject of the main clause. Purdue's dangling-modifier guide explains this correction. Read the whole subject phrase before deciding what it names.

8. Let the timeline determine tense

Actions in the same time frame need consistent tense, but a change in time can require a change in tense. “The town restored the bridge last year, and cyclists use it daily” can be correct: the restoration is past; the use continues. Purdue's tense guidance makes this distinction. Use the surrounding sentences instead of forcing every verb into the same form.

Original grammar practice questions

Replace only the underlined text. Choose A when the original needs no change. Read each complete sentence and any surrounding context.

Question 1

The museum opened a new Start of text to replace: gallery, visitors End of text to replace. lined up before noon.

• A. NO CHANGE
• B. gallery; visitors
• C. gallery visitors
• D. gallery. Although visitors

Question 2

The volunteers needed Start of text to replace: two tools: End of text to replace. a trowel and a rake.

• A. NO CHANGE
• B. two tools;
• C. two tools.
• D. two tools

Question 3

Rina's telescope, which she bought last Start of text to replace: spring has End of text to replace. a removable eyepiece.

• A. NO CHANGE
• B. spring; has
• C. spring has,
• D. spring, has

Question 4

The list of donated Start of text to replace: books are End of text to replace. on the librarian's desk.

• A. NO CHANGE
• B. books have been
• C. books is
• D. books were

Question 5

Three painters shared the studio. A shelf held all three Start of text to replace: painter's End of text to replace. brushes.

• A. NO CHANGE
• B. painters'
• C. painters
• D. painters's

Question 6

The interns spent the afternoon labeling jars, recording measurements, and Start of text to replace: to clean End of text to replace. the workbench.

• A. NO CHANGE
• B. clean
• C. they cleaned
• D. cleaning

Question 7

After checking the map, Start of text to replace: the hikers chose the eastern trail. End of text to replace.

• A. NO CHANGE
• B. the eastern trail was chosen by the hikers.
• C. choosing the eastern trail.
• D. the hikers' decision was to take the eastern trail.

Question 8

On Tuesday, Noor repaired the damaged hinge and Start of text to replace: tests End of text to replace. the gate. By that evening, the repair was complete.

• A. NO CHANGE
• B. will test
• C. tested
• D. testing

Answers and explanations

1. B: gallery; visitors

Both sides are independent clauses, so the semicolon joins them correctly. A uses only a comma. C provides no punctuation between the clauses. D makes the second sentence a dependent fragment beginning with “Although.” This applies the clause-joining rules.

2. A: NO CHANGE

“The volunteers needed two tools” is complete, and the colon introduces those tools. B puts a semicolon before a phrase that cannot stand as a sentence; this is not a complex series requiring semicolons. C leaves a fragment after the period. D removes the punctuation introducing the explanatory list. See the colon and semicolon distinctions.

3. D: spring, has

The clause about when Rina bought the telescope is extra information, enclosed by two commas. A leaves it open. B substitutes a semicolon where the closing comma belongs. C puts the comma after “has,” inside the main clause, rather than at the end of the inserted clause. This follows the paired-comma rule.

4. C: books is

The subject is singular “list,” so “is” fits. A, B and D supply plural verbs: “are,” “have been” and “were.” The plural noun inside “of donated books” does not control agreement. Purdue's intervening-phrase rule explains why.

5. B: painters'

The context explicitly gives three owners. Form plural “painters,” then add the apostrophe. A is singular possessive. C gives the plural without marking possession. D adds apostrophe-s to a regular plural already ending in s. Review the plural-possessive rule.

6. D: cleaning

“Cleaning” matches “labeling” and “recording.” A switches to an infinitive, B to the base form and C to a clause with its own subject. Each breaks the structure of the activities following “spent the afternoon.” This uses parallel grammatical forms.

7. A: NO CHANGE

The hikers checked the map and chose the trail. B makes the trail the subject doing the checking. C leaves the sentence without a main clause. D makes “decision” the subject, but a decision cannot check a map. Apply the logical-subject test.

8. C: tested

“Repaired” and the following sentence establish a past event. “Tested” keeps the coordinated actions in that time frame. A shifts to present and B to future. D leaves “testing” without the structure needed to pair it with “repaired.” See the tense-consistency explanation.

Turn an error into your next practice task

For each missed or uncertain answer, write the rule you needed and explain why your choice failed. If you missed Question 4, for example, write “I matched the verb to books instead of list.” That gives you a specific relationship to check next time.

Then try a full English passage from ACT's official free practice resources. Read the surrounding text when a question depends on meaning. A shorter option can remove necessary information, and a grammatically correct option can still fail to serve the passage's purpose.

Return to the rule when you cannot explain a choice. Once you can, test it on an unfamiliar sentence rather than repeating the same question from memory.

For your next stage of study, explore Sharp's ACT preparation.