Punctuation

Start with Clause Structure

An independent clause contains a subject and finite verb and expresses a complete thought. A dependent clause normally also has a subject and verb, but a subordinating word makes it unable to stand alone: because the office closed. A phrase lacks a complete subject-finite-verb pairing: after the meeting.

Use a comma plus a coordinating conjunction or a semicolon between independent clauses. Use a comma after an introductory dependent clause. Worked example: Although the forecast changed, the event continued begins with a dependent clause. In The forecast changed, the event continued, both parts are independent, so the comma alone creates a comma splice.

Why This Matters: Use language structure and context to choose clear, accurate sentences in academic and everyday writing.

What You Need to Know

Punctuation marks organize writing and clarify meaning. The TEAS focuses on commas, apostrophes, semicolons, and colons.

🧠 Memory Trick

Comma uses: "SICS FANBOYS"

• Series (lists)
• Introductory elements
• Compound sentences (before FANBOYS)
• Separate extra info

FANBOYS: For, And, Nor, But, Or, Yet, So

Commas

1. Lists/Series

Use commas to separate items in a list:

• "The patient reported pain, nausea, and dizziness."
• "Check vitals, administer medication, and document findings."

2. Compound Sentences

Use comma + FANBOYS to join two complete sentences:

• "The patient was stable, but she needed monitoring."
• "The doctor ordered tests, and the nurse drew blood."

No comma needed if only one subject:

• "The nurse checked vitals and documented findings." ✓ (same subject)

3. Introductory Elements

Use a comma after introductory dependent clauses and longer introductory elements. A comma after a short introductory phrase may be optional when the meaning remains clear:

• "After the procedure, the patient rested."
• "However, the test results were delayed."
• "In the morning, we'll reassess."

4. Non-Essential Information (Appositives)

Use commas to set off extra, removable information:

• "Dr. Smith, the cardiologist, will see you tomorrow."
• "The medication, which was prescribed yesterday, helped."

Apostrophes

1. Possession

Singular: Add 's

• "The patient's chart"
• "The nurse's station"

Plural ending in s: Add just '

• "The patients' charts" (multiple patients)
• "The nurses' station" (multiple nurses)

Plural not ending in s: Add 's

• "The children's ward"

2. Contractions

Apostrophe replaces missing letters:

• it is → it's
• do not → don't
• cannot → can't
• will not → won't

Its vs. It's

• Its = possessive (no apostrophe): "The hospital updated its policy."
• It's = it is: "It's time for rounds."

Semicolons

1. Join Related Independent Clauses (without FANBOYS)

• "The patient improved; she was discharged today."
• "The test was positive; treatment began immediately."

2. Separate Items in Complex Lists

When items contain commas:

• "The team includes Dr. Smith, cardiologist; Nurse Jones, RN; and Dr. Lee, oncologist."

Colons

Use After a Complete Sentence to Introduce:

A list:

• "Bring the following items: ID, insurance card, and medication list."

An explanation:

• "The diagnosis was clear: pneumonia."

Do not put a colon between a verb or preposition and its required complement:

• ✗ "The symptoms include: pain and fever."
• ✓ "The symptoms include pain and fever."

✏️ Worked Examples

Example 1: Comma in a Series

WRONG: "The nurse checked vitals documented findings and called the doctor."

Step 1 — Read the sentence and find all the actions (verbs): checked, documented, called. There are three actions happening in a row. That's a series — a list of things.

Step 2 — The rule for lists: put a comma after each item except the last one, and put a comma before "and" when it introduces the final item.

Step 3 — Here's how to add the commas:

• After the 1st item: "checked vitals,"
• After the 2nd item: "documented findings,"
• Before "and" + last item: "and called the doctor"

CORRECT: "The nurse checked vitals, documented findings, and called the doctor."

Why the original was wrong: Without commas, the reader has to work hard to figure out where one action ends and the next begins. In a patient chart, that ambiguity is dangerous.

Example 2: Apostrophe Possession

WRONG: "The patients chart was missing."

Step 1 — Ask: whose chart is this? It belongs to the patient. That means we need a possessive.

Step 2 — The rule for singular possession: add an apostrophe + s ('s) to the owner.

• Owner: patient (singular — one patient)
• Possessive form: patient's

Step 3 — Place it in the sentence.

CORRECT: "The patient's chart was missing."

Why the original was wrong: Without the apostrophe, "patients" looks like a plural noun (more than one patient). But we're not talking about multiple patients — we're talking about one patient's chart. The apostrophe signals ownership.

Contrast with plural possession: If multiple patients shared a chart area, you'd write "the patients' charts" — apostrophe after the s, because the noun is already plural.

Example 3: Semicolon

WRONG: "The patient improved, she went home."

Step 1 — Check both sides of the comma. Is each side a complete sentence on its own?

• "The patient improved" → Yes, complete sentence (subject + verb + complete thought).
• "She went home" → Yes, complete sentence (subject + verb + complete thought).

Step 2 — Two complete sentences joined with just a comma = a comma splice. That's an error.

Step 3 — How to fix a comma splice? You have four options:

1. Replace the comma with a period (make two sentences)
2. Replace the comma with a semicolon
3. Keep the comma but add a FANBOYS conjunction (but, and, so, etc.)
4. Rewrite with a subordinating conjunction (because, after, when, etc.)

The clearest fix here: use a semicolon.

CORRECT: "The patient improved; she went home."

Why a semicolon works: A semicolon joins two closely related complete sentences. These two sentences are definitely related — the improvement led to going home. The semicolon signals that relationship without needing a conjunction.

Example 4: Its vs. It's

WRONG: "The hospital changed it's policy."

Step 1 — See "it's" in the sentence. Ask: what does "it's" mean if you expand it? It's is a contraction for "it is."

Step 2 — Substitute "it is" into the sentence to test it: "The hospital changed it is policy." Does that make sense? No — that's gibberish.

Step 3 — So we need the possessive form, not the contraction. The possessive of "it" is its — no apostrophe. (Possessive pronouns never have apostrophes: its, your, their, whose, our, his, her.)

CORRECT: "The hospital changed its policy."

The test: Whenever you see "it's," mentally replace it with "it is." If the sentence still makes sense, use "it's." If it sounds wrong, use "its."

• "It's time for rounds." → "It is time for rounds." ✓ Makes sense → use "it's"
• "The hospital changed its policy." → "The hospital changed it is policy." ✗ Nonsense → use "its"

💡 Pro Tips

• Choose commas by sentence structure — separate introductory elements, nonessential information, list items, or independent clauses joined by a coordinating conjunction; a speaking pause alone is not a rule.
• Its = possessive; It's = it is or it has — use the expansion test.
• Semicolons join complete sentences — both sides must be independent clauses
• Never put a colon after a verb — "The items are: A, B, C" is wrong
• Editing strategy: Explain each apostrophe or comma by its grammatical function

⚠️ Common Mistakes to Avoid

• Comma splice: "The patient improved, she went home" ✗ (use semicolon or add FANBOYS)
• Its/It's confusion: Its = possessive; It's = it is or it has
• Apostrophe in plurals: "The nurse's attended" ✗ → "The nurses attended" ✓
• Serial-comma style: “Pain, nausea and vomiting” and “Pain, nausea, and vomiting” follow different style choices. Use the serial comma when the specified style requires it or it prevents ambiguity; omission alone is not universally wrong.

Quick Reference

Comma Rules

Apostrophe Rules

Its vs. It's

• Its = belongs to it (possessive)
• It's = it is (contraction)

Punctuation mastered! 💪 Next up: Sentence Structure