Grammar Tips. Comma 15.

The phrase "as well as" usually doesn’t regard commas unless it’s part of a non-restricted clause.

INCORRECT: The pineal gland is the source of both serotonin, as well as melatonin.

CORRECT: The pineal gland is the source of both serotonin as well as melatonin.

What is a non-restrictive clause?

A non-restrictive clause, also known as a non-defining or non-essential clause, is a type of subordinate clause that provides additional information about a noun or pronoun in a sentence. It is not essential to the main meaning of the sentence and can be removed without altering the core message. Non-restrictive clauses are usually set apart by commas.

Here are some examples of sentences with non-restrictive clauses:

1. My best friend, who is a talented musician, just released her first album.

   - The non-restrictive clause "who is a talented musician" provides additional information about "my best friend." It can be removed, and the main sentence would still make sense.

2. The Eiffel Tower, which is located in Paris, is a popular tourist attraction.

   - The non-restrictive clause "which is located in Paris" provides extra information about "The Eiffel Tower." It can be omitted without changing the main point of the sentence.

3. Mark Twain, the author of "The Adventures of Tom Sawyer," was born in Missouri.

   - The non-restrictive clause "the author of 'The Adventures of Tom Sawyer'" adds information about "Mark Twain" but is not necessary for understanding the sentence's main idea.

4. The movie, starring Tom Hanks, won several awards at the film festival.

   - The non-restrictive clause "starring Tom Hanks" provides additional information about "the movie" but is not essential to the sentence's core meaning.

In each of these examples, the non-restrictive clause adds descriptive or explanatory details, but removing it does not affect the basic meaning of the sentence.