Semicolons: Joining Two Complete Sentences

American Diploma › Digital SAT Reading and Writing — Complete Course

What this question type tests

Semicolon questions are part of the Boundaries skill in the Standard English Conventions domain (about 26% of the scored Reading and Writing questions, 11–15 questions). The skill covers punctuation that links clauses and separates list items — and the semicolon does both. It is also one of the favorite wrong answers: test writers put it in the choices because it looks “advanced.”

You get a short passage (25–150 words) with a blank and the stem “Which choice completes the text so that it conforms to the conventions of Standard English?” Typical choices: “rock, it” / “rock; it” / “rock it” / “rock; and it.” You must know exactly when a semicolon is allowed — and it is allowed in only two situations.

Rule 1: A semicolon joins two independent clauses

The teacher's rule: a semicolon joins two independent clauses (two complete sentences) that are closely related. Both sides must be able to stand alone as sentences.

The period test: replace the semicolon with a period. If both parts are still complete sentences, the semicolon is correct. If either part becomes a fragment, the semicolon is wrong.

• ✓ Marble is a metamorphic rock; it forms when limestone is exposed to great heat and pressure.
• ✓ Some desert plants store water in their thick leaves; others store it in underground stems.
• ✓ The museum was full by ten o'clock; visitors had been waiting since dawn.
• ✓ The experiment failed twice; the third attempt succeeded.
• ✗ Because the road was closed; the bus took a longer route. (left side is a dependent clause)
• ✗ The volunteers worked through the night; because the water was rising. (right side is a dependent clause)
• ✗ The team collected samples from forty sites; making it the largest survey of its kind. (right side is a phrase)
• ✗ The tour visited three cities; Luxor, Aswan, and Cairo. (right side is a list, not a clause — use a colon)

Rule 2: Semicolon + conjunctive adverb

Words like however, therefore, as a result, for example, in fact, instead, consequently, moreover, meanwhile are not FANBOYS. They cannot join two clauses with only a comma. When one of them begins the second independent clause, use a semicolon before it and a comma after it (or a period).

• ✓ The bridge was too narrow for modern trucks; therefore, the city built a wider one beside it.
• ✓ The bridge was too narrow for modern trucks. Therefore, the city built a wider one.
• ✗ The bridge was too narrow for modern trucks, therefore, the city built a wider one. (comma splice)
• ✗ The bridge was too narrow for modern trucks therefore, the city built a wider one. (run-on)

But when the adverb sits inside one clause, it is an interrupter and takes a pair of commas — no semicolon: “The second trial, however, was cancelled.” To decide, check what comes before the adverb: a complete sentence (→ semicolon) or just a subject (→ commas).

• ✓ The first trial was a success; however, the second was cancelled. (complete sentence before “however”)
• ✓ The second trial, however, was cancelled. (only the subject before “however”)
• ✗ The second trial; however, was cancelled. (“The second trial” is not a sentence)

Rule 3: No semicolon with FANBOYS between two clauses

A semicolon already does the joining. When you join two independent clauses with for, and, nor, but, or, yet, so, the test's standard choice is a comma before the FANBOYS word.

• ✓ The road was closed, and the bus took a longer route.
• ✓ The road was closed; the bus took a longer route.
• ✗ The road was closed; and the bus took a longer route. (choose “, and” or “;” — not both)

Rule 4: The places a semicolon can never go

Semicolon or something else? Comparing the marks

A semicolon does not change the meaning. It only shows that two complete, related sentences are joined. The relationship between them — addition, result, example, or difference — comes from the words (however, therefore, for example, instead), never from the semicolon itself. So when you choose a semicolon, ask a grammar question (complete + complete?), not a meaning question.

If two choices both look correct — for example a period and a semicolon in the same place — they cannot both be the key. Look for a second difference: a missing comma after “however,” an extra “and,” or a word that turns a clause into a fragment.

Worked examples

Worked example 1 — two independent clauses

Text: Plants that live in very dry places have developed different ways of surviving long periods without rain. Some desert plants store water in their thick, fleshy leaves ______ store it in large underground stems that stay cool below the sand.

Which choice completes the text so that it conforms to the conventions of Standard English?

• A) leaves, others
• B) leaves; others
• C) leaves others
• D) leaves: others,

Answer: B

• A) ✗ Wrong: Both sides are independent clauses (“others store it …” is complete), so a comma alone makes a comma splice.
• B) ✓ Correct: A semicolon joins two closely related independent clauses. Period test: “Some desert plants store water in their thick, fleshy leaves. Others store it …” ✓
• C) ✗ Wrong: No punctuation between two independent clauses is a run-on.
• D) ✗ Wrong: The comma after “others” separates the subject from its verb “store.”

Worked example 2 — conjunctive adverb

Text: The old iron bridge over the canal was built for horse carts, not heavy vehicles. It was too narrow for modern trucks ______ the city built a wider bridge beside it in 2010.

Which choice completes the text so that it conforms to the conventions of Standard English?

• A) , therefore,
• B) ; therefore,
• C) therefore
• D) , therefore

Answer: B

• A) ✗ Wrong: “Therefore” is not a FANBOYS word, so a comma before it creates a comma splice.
• B) ✓ Correct: “It was too narrow for modern trucks” and “the city built …” are both complete; a semicolon before “therefore” and a comma after it is the standard pattern.
• C) ✗ Wrong: With no punctuation, two independent clauses run together.
• D) ✗ Wrong: Comma splice, and the comma after “therefore” is missing too.

Worked example 3 — SAT/ACT extra rule

Text: An international conference for young scientists is held in a different city every year. Over the next three years, the conference will visit Luxor, Egypt ______ Amman, Jordan; and Tunis, Tunisia.

Which choice completes the text so that it conforms to the conventions of Standard English?

• A) Egypt,
• B) Egypt:
• C) Egypt
• D) Egypt;

Answer: D

• A) ✗ Wrong: Each item already contains a comma (“Luxor, Egypt”), and the text later uses “Jordan; and,” so this break must also be a semicolon. A comma makes the list confusing and inconsistent.
• B) ✗ Wrong: A colon cannot be placed in the middle of a list.
• C) ✗ Wrong: With no mark, “Egypt Amman” runs two items together.
• D) ✓ Correct: Semicolons separate list items that contain commas, and this choice is consistent with “Jordan; and Tunis.”

Worked example 4 — when the semicolon is the trap

Text: Scientists recorded water temperatures every week for ten years. They collected samples from forty different sites along the coast ______ the largest survey of its kind in the region.

Which choice completes the text so that it conforms to the conventions of Standard English?

• A) coast; making it
• B) coast, making it
• C) coast. Making it
• D) coast; and making it

Answer: B

• A) ✗ Wrong: The right side (“making it the largest survey …”) is a participle phrase, not a clause, so a semicolon is wrong.
• B) ✓ Correct: A comma attaches the participle phrase to the complete sentence before it.
• C) ✗ Wrong: The period leaves “Making it the largest survey of its kind in the region.” as a fragment.
• D) ✗ Wrong: A semicolon + “and” before a phrase: two errors.

Practice

Ten original Digital SAT-style questions. Do the period test on every semicolon you see.

All pages in this course

Start here

• The Digital SAT: Complete Overview
• Time Strategy and How to Attack Every Question

Craft and Structure

• Words in Context
• High-Value Vocabulary for SAT Reading and Writing
• Text Structure and Purpose
• Cross-Text Connections

Information and Ideas

• Central Ideas and Details
• Command of Evidence: Textual
• Command of Evidence: Quantitative
• Inferences

Standard English Conventions

• Sentence Boundaries
• Extra Information: Commas, Dashes and Brackets in Pairs
• Commas: Introductions, Lists, Adjectives — and When NOT to Use One
• Semicolons: Joining Two Complete Sentences
• Colons: After a Complete Sentence
• Dashes — and Choosing Between , ; : —
• Subject–Verb Agreement
• Pronoun–Antecedent Agreement, Clarity and Consistency
• Pronoun Case and Sound-Alike Pronouns
• Verb Tense and Aspect
• Verb Finiteness: Gerunds, Participles and Infinitives
• Dangling and Misplaced Modifiers
• Parallel Structure
• Faulty and Logical Comparisons
• Plurals and Possessives

Expression of Ideas

• Transitions
• Rhetorical Synthesis (Student Notes)

Full practice tests

• Digital SAT Reading and Writing — Practice Test 1
• Digital SAT Reading and Writing — Practice Test 2
• Digital SAT Reading and Writing — Practice Test 3