Do you use a comma after an introductory phrase beginning with the word as?

You generally use a comma after an introductory phrase beginning with "as" if the phrase is more than four words long and acts as a modifier for the main clause.

Here are some examples:

With a comma:

* As a matter of fact, the meeting was canceled.

* As the sun began to set, the sky turned a brilliant orange.

* As you may know, I'm moving to a new city next month.

Without a comma:

* As soon as I get home, I'm going to bed.

* As long as you're happy, I'm happy.

Note: If "as" introduces a dependent clause (a clause that cannot stand alone as a sentence), a comma is always required.

Example:

* As I was walking down the street, I saw a dog chasing a squirrel.

Exceptions:

* Sometimes, even if the phrase is longer than four words, a comma is not necessary if the phrase is closely connected to the main clause and doesn't create ambiguity.

* If "as" introduces a direct address or a parenthetical element, you do not need a comma.

Examples:

* As you know, this is a very important project. (direct address)

* As a matter of fact, I think this is a good idea. (parenthetical)

Ultimately, the best way to decide whether to use a comma is to read the sentence aloud and listen for natural pauses. If you pause after the phrase, it's likely that a comma is needed.