Comprised vs. Composed | Difference & Examples

The related verbs comprise and compose, as well as their past tenses comprised and composed, are commonly confused:

  • Comprise means “to be made up of.” The whole of something comprises its parts.
  • Compose means “to make up.” The parts of something compose the whole.
  • The passive phrasing is composed of is correct and means the same thing as “comprises” on its own. The phrase “is comprised of” is a common mistake.
Examples: Comprise in a sentence Examples: Compose in a sentence
The university comprises a number of different campuses. The university is composed of a number of different campuses.
His education comprised deep study of Greek, Latin, philosophy, and mathematics. Many fresh ingredients compose this delicious sandwich.

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Comma Before Which | Rules & Examples

“Which” is a relative pronoun used to introduce a relative clause. Whether you need a comma before “which” depends on which kind of relative clause it introduces:

  • You need a comma before “which” when it introduces a nonrestrictive clause: a clause providing extra information that isn’t essential to the sentence’s meaning.
  • There’s no comma before “which when it introduces a restrictive clause: a clause that couldn’t be removed without changing the sentence’s meaning.
Examples of when to use a comma before “which”
“Which” introducing a nonrestrictive clause (comma) “Which” introducing a restrictive clause (no comma)
My car, which is a blue Ford Focus, was stolen last week. The car which was reported stolen was a blue Ford Focus.
I can’t wait for Christmas, which is my favorite holiday. The subjects which I struggle most with are chemistry and history.
Tip
The easiest way to check whether a comma is needed is to see what the sentence looks like without the “which” clause:

  • If it still expresses the same meaning (e.g., “My car was stolen last week”), you need the comma.
  • If it means something less specific (e.g., “The car was a blue Ford Focus”; what car?), no comma is needed.

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Comma Before Such As | Rules & Examples

The prepositional phrase “such as” is used to introduce examples or to specify something about the phrase it modifies.

  • There’s a comma before “such as” when it introduces examples that could be left out.
  • There’s no comma before “such as” when it introduces essential identifying information
Examples of when to use a comma before “such as”
“Such as” introducing examples (comma) “Such as” introducing identifying information (no comma)
Many types of animals, such as fish and seabirds, live in marine environments. Animals such as dogs and cats make good household pets.
The book touches on a number of complicated topics, such as music theory, brain chemistry, and artificial intelligence. I enjoy learning about topics such as history and technology.
Tip
Try a simple trick to confirm whether you need a comma: remove the “such as” phrase. If the sentence still expresses the same basic meaning, add the comma. If not, no comma is needed. When in doubt, double-check with the punctuation checker.

“The book covers a number of complicated topics” expresses the same point as the original sentence, but “I enjoy learning about topics” is so vague that it’s not really expressing any clear point. The “such as” clause is essential in the latter sentence, so there’s no comma.

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Comma Before or After So | Rules & Examples

When using the conjunction “so” to connect two clauses, you can tell whether to add a comma before it with a simple trick:

  • When “so” could be replaced with “therefore,” use a comma before “so.”
  • When “so” could be replaced by “so that,” don’t add a comma.
Examples of when to use a comma before “so”
“So” meaning “therefore” (comma) “So” meaning “so that” (no comma)
I was hungry, so I ate some chips. Maria is saving up so she can move out.
I was hungry. Therefore, I ate some chips. Maria is saving up so that she can move out.
Note
“So” also has a variety of other uses in which it isn’t classed as a conjunction but instead as an adverb or another part of speech. In these uses, there’s generally no comma needed (e.g., “I think so,” “there’s only so much time,” “say it’s not so”).

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Comma Before Too | Rules & Examples

You don’t need to add a comma before “too” in most contexts. You can add one if you want to place more emphasis on “too,” but it’s not mandatory:

  • Your brother is coming with us too.
  • Your brother is coming with us, too.

You do need commas before and after “too” when it appears between a verb and its object:

  • I expect too that you’ll want something to eat in the morning.
  • I expect, too, that you’ll want something to eat in the morning.

You also need a comma after “too” when it’s used to introduce a sentence (although we don’t recommend using “too” in this way regardless):

  • Too we consider the implications of our study for other researchers.
  • Too, we consider the implications of our study for other researchers.
Note
Similar considerations apply when deciding whether to use a comma before “such as,” a comma before or after “however,” a comma before “as well as,” or a comma before “which.”

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Comma Before As Well As | Rules & Examples

As well as is an expression meaning “in addition to.” In most contexts, you don’t need a comma before “as well as.”

Example: No comma before “as well as”
Marta is a great dancer as well as an accomplished singer.

You can optionally add a comma before “as well as” if you want to place less emphasis on the phrase that comes after it.

Example: Comma before “as well as” to shift emphasis
He had some reservations about their ideas, as well as their tactics.

But you need a comma before and after the “as well as” phrase when it comes straight after the subject of the sentence.

  • His mother as well as his father encouraged him to believe in himself.
  • His mother, as well as his father, encouraged him to believe in himself.
Note
Similar considerations apply when deciding whether to use a comma before “such as,” a comma before or after “however,” a comma before “too,” or a comma before “which.”

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Serial Comma | Rules, Examples & Definition

The serial comma (aka Oxford comma or Harvard comma) is a term that describes the use of a comma before the conjunction in a list of three or more items (e.g., the comma before “and” in “pancakes, scrambled eggs, and bacon”). The name comes from the fact that it’s used in a series (list).

The serial comma is optional—it’s not an error to leave it out or to include it. Different style guides and publishers have different recommendations, but academic style guides normally recommend using it.

If you need to follow a particular style, check out our quick summary of who recommends the serial comma below. If you don’t, the choice is up to you. Just write according to your own preference.

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Comma Before While | Rules & Examples

The word “while” has a couple of different meanings. Depending on which meaning you intend, you may or may not need a comma before “while.”

If you’re using “while” to mean “during the time that,” you don’t need a comma.

Example: “While” meaning “during the time that”
Please don’t distract me while I’m working.

If you’re using “while” to mean “although” or “whereas,” you need a comma.

Example: “While” meaning “whereas”
Some people enjoy traveling, while others prefer to stay home.
Note
Similar rules apply to other subordinating conjunctions: commas before “because” and commas before “as well as.”

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Comma Before Because | Rules & Examples

You normally shouldn’t use a comma before “because” when the reason that “because” introduces is essential to your meaning. For example, the point of the sentence below is to give a reason for good grammar’s importance.

Examples: “Because” introducing essential clause
Good grammar is important because it allows you to express yourself clearly.

When you add a comma before “because,” it removes the emphasis from the reason it introduces. The main point of the sentence below is simply to state the importance of good grammar; the reason is an afterthought.

Examples: Comma before “because”
Good grammar is important, because it allows you to express yourself clearly.
Note
Similar rules apply to other subordinating conjunctions: commas before “while” and commas before “as well as.”

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Oxford Comma | Definition, Examples & When to Use

The Oxford comma (also known as the serial comma or Harvard comma) is the use of a comma before the conjunction in a list of three or more items (e.g., the comma before “and” in “paints, brushes, and canvas”). The name comes from the fact that it’s recommended by Oxford University Press.

The Oxford comma is optional—it’s not a grammatical error to leave it out or to include it. Different style guides and publishers have different recommendations about its use, though major style guides recommend using it more often than not.

If you need to follow a particular style guide, check out our quick summary of who recommends the Oxford comma below. If you don’t, the choice is up to you; just write according to your own preference.

Oxford Comma

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