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📝 English and Language Usage · Conventions of Standard English · Lesson 2 of 6 · 6 min

Comma rules: lists, compound sentences, introductions and extras

🔢 Commas cause more lost points than any other mark. Six rules cover almost every comma you will ever need on the TEAS.

💡 Key idea

Use commas for lists, before a conjunction joining two full sentences, after introductions and around extra information.

🧠 The idea

1. LISTS: separate three or more items: "gauze, tape, and gloves." The comma before "and" (the serial comma) is acceptable and common; just be consistent. 2. COMPOUND SENTENCES: put a comma before a coordinating conjunction (for, and, nor, but, or, yet, so) that joins two independent clauses: "The bus was late, so we walked." No comma if the second part has no subject: "We waited and then walked." 3. INTRODUCTORY ELEMENTS: "After the meeting, we ate." 4. NONESSENTIAL CLAUSES and phrases get a pair of commas; essential ones get none: "My brother, who lives in Ohio, is a medic" (I have one brother) vs. "Students who study pass." 5. APPOSITIVES that rename a noun: "Dr. Lane, our dentist, retired." 6. DATES and ADDRESSES: "On May 4, 2025, in Dayton, Ohio, the clinic opened." Never put a single comma between a subject and its verb.

✏️ Worked example

Punctuate: "When the storm ended the nurses who had worked all night went home and the day shift took over." Step 1: "When the storm ended" is an introductory clause, so add a comma after it. Step 2: "who had worked all night" tells WHICH nurses went home, so it is essential: no commas. Step 3: "the day shift took over" is a complete sentence joined by "and," so add a comma before "and." Result: "When the storm ended, the nurses who had worked all night went home, and the day shift took over."

📌 Takeaways

  • Comma + FANBOYS joins two complete sentences.
  • Extra (nonessential) information gets a pair of commas; essential information gets none.
  • Never separate a subject from its verb with one comma.

✅ Check yourself

Question 1 of 3

Which sentence is punctuated correctly?

  1. The clinic, opens at eight and closes at five.
  2. The clinic opens, at eight and it closes at five.
  3. The clinic opens at eight, and it closes at five.
  4. The clinic opens at eight and, it closes at five.
Show the answer and rationale

Answer: C

Two independent clauses joined by "and" take a comma before the conjunction. The other choices put the comma after "and," between the subject and verb, or in the middle of a clause.

Question 2 of 3

Which sentence correctly sets off a nonessential clause?

  1. Ms. Ortiz, who teaches biology coaches soccer.
  2. Ms. Ortiz who teaches biology, coaches soccer.
  3. Ms. Ortiz who teaches biology coaches, soccer.
  4. Ms. Ortiz, who teaches biology, coaches soccer.
Show the answer and rationale

Answer: D

A named person is already identified, so "who teaches biology" is extra information and needs a comma on both sides. Using only one comma, or a comma between the verb and its object, is incorrect.

Question 3 of 3

Where does the comma belong? "On March 3 2024 the new wing opened."

  1. Only after "3"
  2. Only after "2024"
  3. After "3" and after "opened"
  4. After "3" and after "2024"
Show the answer and rationale

Answer: D

In a month-day-year date, a comma follows the day and another follows the year when the sentence continues: "On March 3, 2024, the new wing opened." Leaving out either comma, or adding one before the period, is wrong.

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