What do you call it when start a sentence with first followed by comma?

There isn't a specific term for starting a sentence with "first" followed by a comma. It's a common way to begin a list, but it's not a grammatical structure with its own name.

Here's a breakdown:

* "First" as an introductory word: It often signals the start of a list or enumeration.

* Comma after "first": This separates the introductory word "first" from the rest of the sentence, creating a smooth transition.

Example:

* First, we need to gather the materials.

* Then, we can start building the project.

Instead of a specific term, you can describe the structure as:

* A sentence beginning with an introductory word followed by a comma.

* A sentence using a comma after an introductory element.

Let me know if you have any other grammar questions!