Key Takeaways
- Use commas in lists, before coordinating conjunctions joining clauses, and after introductory elements
- Semicolons join closely related independent clauses without a conjunction
- Apostrophes show possession and form contractions—"its" (possessive) vs. "it's" (it is)
- Colons introduce lists or explanations after a complete sentence
- Periods and commas go inside quotation marks in American English
Last updated: January 2026
Punctuation
Correct punctuation ensures clarity in writing. The TEAS tests your knowledge of commas, semicolons, colons, apostrophes, and other punctuation marks.
Commas
Use commas in these situations:
| Rule | Example |
|---|---|
| Between items in a list | She checked vitals, gave medications, and updated charts. |
| Before coordinating conjunction joining independent clauses | The patient improved, and she was discharged. |
| After introductory elements | After the surgery, the patient rested. |
| Around non-essential information | The nurse, who was new, performed well. |
| Between coordinate adjectives | She was a skilled, compassionate nurse. |
| In dates, addresses, titles | June 15, 2026; Chicago, Illinois |
| With direct address | Doctor, the patient is ready. |
Do NOT use commas:
- ❌ Between subject and verb: "The nurse, administered medication."
- ❌ Before "that" introducing essential clauses: "The patient, that arrived first."
- ❌ After coordinating conjunctions: "The nurse helped, but, the patient refused."
Semicolons
Use semicolons:
| Rule | Example |
|---|---|
| Between closely related independent clauses | The surgery was successful; the patient is recovering well. |
| Before conjunctive adverbs | She was tired; however, she continued working. |
| In lists with internal commas | Offices are in Boston, MA; Denver, CO; and Seattle, WA. |
Colons
Use colons:
| Rule | Example |
|---|---|
| Before a list | She needs: gauze, tape, and scissors. |
| Before an explanation | The diagnosis was clear: pneumonia. |
| After a greeting in formal letters | Dear Dr. Smith: |
| Between hours and minutes | 3:30 PM |
Note: A complete sentence should precede the colon when introducing a list.
Apostrophes
Use apostrophes for:
| Rule | Example |
|---|---|
| Possession (singular) | The nurse's station |
| Possession (plural ending in s) | The nurses' lounge |
| Possession (plural not ending in s) | The children's ward |
| Contractions | don't, can't, it's (it is) |
Common Errors:
| Correct | Incorrect | Explanation |
|---|---|---|
| its (possessive) | it's (when meaning possession) | "Its" = possessive; "it's" = "it is" |
| their (possessive) | they're (when meaning possession) | "Their" = possessive; "they're" = "they are" |
| whose (possessive) | who's (when meaning possession) | "Whose" = possessive; "who's" = "who is" |
Quotation Marks
Use quotation marks for:
- Direct quotes: She said, "The patient is stable."
- Titles of short works: articles, short stories, poems
Punctuation placement:
- Periods and commas go INSIDE quotation marks
- Semicolons and colons go OUTSIDE
- Question marks depend on whether the quote is a question
Hyphens and Dashes
| Mark | Use | Example |
|---|---|---|
| Hyphen (-) | Compound adjectives before nouns | well-known doctor, 10-year-old patient |
| Hyphen (-) | Compound numbers | twenty-one, three-fourths |
| En dash (–) | Number ranges | pages 15–20, 2024–2026 |
| Em dash (—) | Abrupt break or emphasis | The result—surprisingly—was positive. |
Other Punctuation
| Mark | Use | Example |
|---|---|---|
| Parentheses ( ) | Additional information | The medication (50 mg) was given. |
| Brackets [ ] | Within quotes to add/clarify | She said, "[The patient] is stable." |
| Ellipsis (...) | Omitted words or pause | "The results were... inconclusive." |
Common Punctuation Errors
| Error | Incorrect | Correct |
|---|---|---|
| Comma splice | She arrived, she checked vitals. | She arrived, and she checked vitals. |
| Missing comma after intro | After the surgery the patient rested. | After the surgery, the patient rested. |
| Its vs. it's | The hospital changed it's policy. | The hospital changed its policy. |
| Unnecessary apostrophe | The nurse's checked the patient's. | The nurses checked the patients. |
Test Your Knowledge
Which sentence uses the semicolon correctly?
A
B
C
D
Test Your Knowledge
Which sentence correctly uses an apostrophe?
A
B
C
D
Test Your Knowledge
Where should a comma be placed in this sentence: "After the examination the doctor wrote the prescription."
A
B
C
D