We sometimes begin a sentence with an introductory phrase. Here are some examples:
At the moment
Under the kitchen table
After dinner
In the morning
When you begin a sentence with a phrase like this, you must follow the phrase with a comma. The comma sets the phrase apart from the rest of the sentence.
Look at these same phrases attached to a complete sentence:
At the moment, we have no money for eating out.
Under the kitchen table, we found lots of crumbs.
After dinner, we will take a walk.
In the morning, everything will seem better.
Always use a comma after an introductory phrase at the start of a sentence.
It’s your turn. Place a comma into this sentence: Before school I need to finish my homework. Did you figure it out? Good for you.