Commas, Periods, Question Marks: Grammar Fundamentals Notes for IEO (English Olympiad)

Grammar Fundamentals

Topic: Commas, Periods, Question Marks
Program: IEO (English Olympiad)

Punctuation	What it does	When to use it
Comma ( , )	Separates parts of a sentence to make meaning clear.	• Between items in a list • After introductory words/phrases • Before conjunctions (and, but, or, nor, for, so, yet) in compound sentences • To set off non‑essential clauses or appositives
Period ( . )	Marks the end of a declarative sentence.	• After a complete thought • At the end of a sentence that ends with a quotation or parenthetical
Question Mark ( ? )	Marks a direct question.	• At the end of an interrogative sentence (yes/no, wh‑questions, tag questions)

Tip: Think of a comma as a pause, a period as a full stop, and a question mark as a raised pitch.

Listing Items
“I bought apples, bananas, oranges, and grapes.”
The serial (Oxford) comma before “and” is optional but helps avoid ambiguity.
Introductory Elements
“After the meeting, we went to lunch.”
Also after introductory adverbials: “Unfortunately, the test was postponed.”
Compound Sentences
“I wanted to go, but it started raining.”
The comma before the coordinating conjunction is required.
Non‑essential Clauses / Appositives
“My brother, who lives in London, is visiting.”
If the clause can be removed without changing the core meaning, set it off with commas.
Direct Address & Quotations
“Lisa, could you pass the salt?”
“He said, “I’m ready.””

End of Sentences
“She finished her homework.”
After Abbreviations
“She lives in U.S.A.” (Note: Some style guides omit the period after “U.S.” but include after “U.S.A.”)
In Complex Structures
“We will leave by 5 p.m., and you should be ready.”

Sentence with all three marks

“After the rain stopped, the children went outside, and they built a sandcastle, but the dog didn’t want to join; why not?”

Word/Clause	Function	Punctuation
After the rain stopped	Introductory clause	Comma after “stopped”
the children went outside	Main clause	Period after “outside”
and they built a sandcastle	Compound clause (connected by “and”)	Comma before “and”
but the dog didn’t want to join	Contrast clause	Comma before “but”
why not	Rhetorical question	Question mark

Result:

“After the rain stopped, the children went outside, and they built a sandcastle, but the dog didn’t want to join; why not?”

Punctuation	Usage	Quick Check
Comma	1️⃣ list items 2️⃣ intro clauses 3️⃣ compound sentences 4️⃣ non‑essential info	Does a pause help clarity?
Period	End of a complete thought	Is this the end of the sentence?
Question Mark	End of a direct question	Is the sentence asking something?

Mnemonic:

Rewrite the following without punctuation, then add commas, periods, and question marks correctly.

after the game we celebrated because we won we also bought ice cream

Answer:

After the game, we celebrated because we won. We also bought ice cream.

Feel free to test yourself with similar sentences!