ACT English 3: Sentence Structure

Sentence and clause structure

The classification of sentences according to the number and types of clauses in their syntactic structure.

What is an independent clause?

A clause that contains a subject and a predicate and can stand alone as a grammatically complete sentence.

What is a dependent clause?

A clause that contains a subject and verb but cannot stand alone as a complete sentence. It is typically introduced by a subordinating conjunction, relative pronoun, or similar subordinating word.

Which five basic clause patterns are commonly identified in English?

The patterns are: subject–intransitive verb; subject–transitive verb–object; subject–linking verb–subject complement; subject–transitive verb–indirect object–direct object; and subject–transitive verb–object–object complement.

Subject–intransitive verb clause pattern

This pattern contains a subject and a verb that does not take a direct object, as in “The students laughed.”

Subject–transitive verb–object clause pattern

This pattern contains a subject, a verb that takes a direct object, and the object receiving the action, as in “The students solved the problem.”

Subject–linking verb–subject complement clause pattern

A linking verb connects the subject to a complement that identifies or describes it. For example, “The solution is acidic,” where “acidic” is an adjective complement.

Subject–verb–indirect object–direct object clause pattern

A transitive verb is followed by a recipient and a thing transferred or affected, as in “The instructor gave the class an assignment.” This often corresponds to a prepositional form such as “gave an assignment to the class.”

Subject–verb–object–object complement clause pattern

The verb affects an object and establishes a description or identity for that object, as in “The experiment made the solution cloudy.” The object and its complement function together as a syntactic unit.

Simple sentence

A sentence containing exactly one independent clause and no dependent clause. It may still contain compound subjects, compound predicates, or multiple phrases.

Why is “The dog barked and howled in the yard” a simple sentence rather than a compound sentence?

It has one subject and one independent clause with a compound predicate, “barked and howled.” A compound predicate does not create multiple independent clauses.

Compound sentence

A sentence containing at least two independent clauses. It does not need to contain a dependent clause.

Which coordinating conjunctions can join independent clauses in a compound sentence?

The coordinating conjunctions are for, and, nor, but, or, yet, and so. They are commonly remembered as FANBOYS.

How can a semicolon correctly join two independent clauses?

A semicolon can connect closely related independent clauses without a coordinating conjunction, as in “The reaction ended; the solution cooled.”

When can a colon join two independent clauses?

A colon may separate two independent clauses when the second explains, illustrates, or elaborates on the first, as in “One conclusion was clear: the evidence was insufficient.”

How is a conjunctive adverb used between independent clauses?

The clauses are separated by a semicolon, and the conjunctive adverb is followed by a comma: “The sample was contaminated; therefore, the data were discarded.”

Comma splice

An error in which two independent clauses are joined only by a comma, as in “The solution changed color, the reaction was complete.” It can be corrected with a period, semicolon, or comma plus a coordinating conjunction.

Complex sentence

A sentence containing at least one independent clause and at least one dependent clause. The dependent clause may come before or after the independent clause.

Compound-complex sentence

A sentence containing at least two independent clauses and at least one dependent clause.

Adverbial clause

A dependent clause that modifies a verb or the main clause by specifying information such as time, place, cause, condition, or manner. For example, “When the trial ended” indicates when an action occurred.

Relative clause

A dependent clause that modifies a noun or noun phrase, functioning similarly to an adjective. It is often introduced by a relative pronoun such as who, which, or that.

Restrictive versus nonrestrictive relative clause

A restrictive relative clause identifies which noun is meant and is essential to the meaning; it is generally not set off by commas. A nonrestrictive relative clause adds nonessential information and is set off by commas.

Noun clause

A dependent clause that functions as a noun. It can serve as a subject, object, predicate nominative, or appositive.

Sentence fragment

A group of words that is not a complete sentence because it lacks an independent clause, a required grammatical element, or a complete thought.

Why is “Swimming in the ocean” often an -ing fragment?

In this form, “swimming” functions as a gerund or noun-like word rather than a finite verb, and the group lacks a complete subject–verb structure. It could become complete as “They were swimming in the ocean.”

Does beginning a sentence with “and” or “but” automatically make it a fragment?

No. A sentence beginning with a conjunction can still be grammatically complete if it contains an independent clause; treating every such sentence as incomplete is a style prescription rather than a grammatical rule.

Run-on sentence

A sentence in which two or more independent clauses are joined without appropriate punctuation or coordination. Run-ons include fused sentences and, in many usage systems, comma splices.

Fused sentence

A run-on sentence in which independent clauses are placed together with no separating punctuation, as in “The solution boiled we stopped heating.”

How can the fused sentence “The reaction ended we recorded the result” be corrected?

Possible corrections include “The reaction ended. We recorded the result,” “The reaction ended, and we recorded the result,” “The reaction ended; we recorded the result,” or “The reaction ended—we recorded the result.”

Can a run-on sentence be very short?

Yes. Length is not required: “I drive, she walks” is a comma splice, and “I drive she walks” is a fused sentence because each subject is paired with an independent clause.

What distinguishes a compound sentence from a sentence with a compound predicate?

A compound sentence has two or more independent clauses, usually with separate subjects and predicates. A compound predicate has one independent clause with multiple verbs sharing a subject.