Using Commas with Intro Words

Some sentences start with intro words.

In writing each project is like a journey.

       ("In writing" introduces the sentence.)

When you have four or more intro words, place a comma after them.

For a long journey, you start by gathering everything you'll need on the trail.

       (A comma follows "For a long journey.")

Readers are looking for the main part of the sentence, with a subject + verb pattern. The comma signals that the main part of the sentence is starting.