9.1 Coordinating conjunctions and compound sentences

Coordinating Conjunctions

Seven Coordinating Conjunctions and Their Functions

The seven coordinating conjunctions connect words, phrases, and clauses of equal grammatical weight. The mnemonic FANBOYS is the quickest way to remember all seven:

• For – gives a reason or explanation (I brought an umbrella, for it might rain.)
• And – adds information or combines ideas (She likes coffee and tea.)
• Nor – adds a negative alternative (He doesn't eat meat, nor does he consume dairy.)
• But – shows contrast or an unexpected outcome (The movie was long but entertaining.)
• Or – presents alternatives or choices (Would you prefer coffee or tea?)
• Yet – introduces contrast, similar to "but" with a slightly stronger surprise (He's tired, yet he continues working.)
• So – indicates a result or consequence (It was raining, so we stayed indoors.)

Notice that nor flips the word order in the second clause ("nor does he"), much like a question. That's a common trip-up on quizzes.

In compound sentences, these conjunctions do three things:

• Join independent clauses into grammatically complete thoughts
• Give both clauses equal emphasis, so neither idea feels more important than the other
• Signal the logical relationship between the two ideas (addition, contrast, cause-effect, etc.)

Creating Compound Sentences

A compound sentence follows a specific pattern:

Each clause must be able to stand on its own as a complete sentence. For example: I love coffee, and I drink it every morning. Both "I love coffee" and "I drink it every morning" work as independent sentences.

Choosing the right conjunction:

1. Identify the relationship between your two ideas (Are you adding? Contrasting? Showing a result?).
2. Pick the FANBOYS word that matches that relationship.
3. Read the sentence aloud to confirm the conjunction conveys what you actually mean.

Using the wrong conjunction can change your meaning entirely. Compare: She studied hard, so she passed vs. She studied hard, but she passed. The second version implies passing was surprising, which probably isn't what you intended.

Punctuation rules:

• Place a comma before the coordinating conjunction when it joins two independent clauses. (The trail was steep, but the view was worth it.)
• You can omit the comma when both clauses are very short and closely related. (She sang and he danced.)
• Do not place a comma before a conjunction that joins only two words or phrases. (She likes coffee and tea needs no comma because "tea" isn't an independent clause.)

Relationships Between Independent Clauses

Each conjunction signals a different type of relationship:

• Addition (and) – combines related ideas: I like apples, and I enjoy oranges.
• Contrast (but, yet) – highlights differences or surprises: He studied hard, but he failed the test.
• Choice (or) – presents alternatives: We can go to the beach, or we can stay home.
• Cause-effect (for, so) – shows reasoning or results: The sun was setting, so we headed back home.
• Negative addition (nor) – adds negative information: She doesn't like coffee, nor does she drink tea.

For your sentences to read clearly, keep a few things in mind:

• The two clauses should be logically connected. Don't join unrelated ideas just because you can. (I like pizza, and the sky is blue is grammatically correct but confusing.)
• Keep tense and subject-verb agreement consistent across both clauses. (He plays guitar, and she sings — both present tense.)
• Aim for roughly similar length in both clauses. A three-word clause paired with a twenty-word clause can feel lopsided.
• Vary the conjunctions you use. If every sentence in a paragraph starts with "and," the writing gets monotonous fast.

Compound vs. Other Sentence Structures

Understanding where compound sentences fit among the four sentence types helps you use them intentionally:

• Simple sentence – one independent clause, no conjunction joining clauses: The cat slept on the windowsill.
• Compound sentence – two or more independent clauses joined by a coordinating conjunction: I woke up late, but I still made it to work on time.
• Complex sentence – one independent clause + one or more dependent clauses, joined by a subordinating conjunction: Although it was raining, we went for a walk.
• Compound-complex sentence – two or more independent clauses + at least one dependent clause: When the alarm rang, I woke up, and I got ready for work.

You can also join independent clauses without FANBOYS:

• Semicolon alone: I love chocolate; my sister prefers vanilla.
• Semicolon + conjunctive adverb: It was raining; however, we still went to the park.

These alternatives are covered more in later sections, but for now just know that a semicolon replaces both the comma and the coordinating conjunction. Don't use both together (I love chocolate; but my sister prefers vanilla is incorrect in standard usage).