Understanding the Introductory Comma

1. What Is an Introductory Clause?

An introductory clause is a dependent clause that comes before the main (independent) clause in a sentence.

It usually begins with a subordinating conjunction, such as:

after
although
because
before
if
since
when
while

Examples of Introductory Clauses

When the game ended,
Because the update launched early,
Although the player was injured,

These clauses set up context, but they do not express a complete thought on their own.

2. AP Style Rule: Always Use a Comma After an Introductory Clause

Whenever a dependent clause comes at the beginning of a sentence, AP Style requires a comma before the independent clause.

Formula

Introductory Clause + , + Independent Clause

Examples

When the trailer dropped, fans reacted instantly.
Because the update failed, the company released a patch.
Although the weather was terrible, the team continued playing.
If the player recovers, he will start tonight.

This comma signals a natural pause and prevents misreading.

3. Why This Comma Matters

This rule is essential for clarity, pacing, and SEO.

A. Prevents Misreading

Without the comma, readers may misinterpret the sentence.

Incorrect:

When the game ended the fans celebrated.

(Feels rushed and unclear)

Correct:

When the game ended, the fans celebrated.

B. Improves Readability

Introductory clauses add context.

The comma helps readers process that context before moving on.

C. Strengthens SEO

Google rewards:

Clean syntax
Clear relationships
Easy‑to‑parse sentences

Introductory commas help search engines understand sentence structure.

D. Supports Professional Tone

Every newsroom — especially AP Style — expects this comma.

Skipping it looks amateur.

4. Types of Introductory Elements That Require a Comma

It’s not just clauses. AP Style requires commas after any introductory element that is long or creates a natural pause.

A. Introductory Dependent Clauses

When the update launched, users installed it immediately.

B. Introductory Phrases

Prepositional Phrase

In the final seconds, the player scored.

Infinitive Phrase

To win the game, the team trained hard.

Participial Phrase

Running down the field, the player scored.

C. Introductory Words

Yes, the update is available.

Well, that was unexpected.

However, the patch didn’t fix everything.

5. When You Do NOT Need a Comma

AP Style allows you to skip the comma only when the introductory phrase is:

Very short
Not essential
Not likely to confuse the reader

Examples (Comma Optional)

In 2025 the company expanded.
At noon the team practiced.

But even here, using the comma is often clearer.

6. Examples in Real Article Writing

Before (Incorrect)

Because the update launched early users reported issues.

After (Correct)

Because the update launched early, users reported issues.

Another Example

Before:

When the player missed the shot the crowd gasped.

After:

When the player missed the shot, the crowd gasped.

One More Example