When it comes to writing a memo, composing a business email, or preparing a PowerPoint presentation, the details may not be critical enough to warrant hiring an editor or talented copywriter to whisper tips and tricks into your ear. The important part is what you’re trying to convey, right? Well, presentation is still critical, and grammar is a part of clear and precise presentation. If you’re submitting articles as a freelancer or attempting to get a creative piece published, issues can seem even more egregious.

While many are proficient at written communication, only making tiny errors few and far between, a misplaced comma could be the difference between ‘stellar’ and ‘good’ output, especially for writing, communication, and marketing fields. By learning these three comma rules, you’ll have a handle on the punctuation mistakes people notice most often.

Coordinating Conjunctions

When two complete sentences (i.e. containing both subject and verb) are joined with a coordinating conjunction, a comma precedes the conjunction.


I went to the fair. I bought cotton candy. Both are complete sentences, so a comma is necessary before the ‘and.’

Coordinating conjunctions include ‘for,’ ‘and,’ ‘nor,’ ‘but,’ ‘or,’ and ‘so’ (or FANBOYS). ‘Because,’ ‘since,’ and ‘as’ are not coordinating conjunctions and do not get commas.



Comma Splicing

The term comma splice refers to any extra comma that erroneously splits a sentence. Because many people are wary of using the full stop finality of a period or want to add punctuation to indicate a pause, comma issues abound.

Comma splicing is definitely related to the coordinating conjunction rule, but I feel that it qualifies as its own animal. FANBOYS only receive commas when both phrases are complete sentences with both subject and verb. Never split a subject and its verb regardless of the conjunction present.

No comma is needed. I went and bought. ‘I’ is the subject for both verbs.


The second comma splice can happen, though, even when the two phrases are complete sentences. Just because a period may feel too staccato to use does not mean it’s interchangeable with a comma. This often happens in the absence of a coordinating conjunction, and I see it frequently in ad copy.


‘Thank you’ stands alone. ‘Come again’ is an imperative sentence. Together, they’d more correctly be written as ‘Thank you. Come again,’ or ‘Thank you; come again.’ This is becoming less of a norm, however, and could be phased out completely as rules evolve.

Subordinate Clauses

A subordinate or dependent clause is not a complete thought but rather acts as supplemental information for the main thought. These typically start with a subordinate conjunction (but NOT our coordinating FANBOYS).



Some subordinate clauses can be complex, so be careful to properly punctuate those, too. Treat them as mini-sentences and evaluate whether phrases can stand on their own or be offset with commas.

But seriously, though. Who would do such a thing. Share? Pfft.




Despite an ‘and’ being present in both of the above phrases, the two things the subordinate clause is discussing are both dependent on the usage of ‘whether’/’if.’ Therefore, no comma is used. Doing so would split the subordinate clause and cause confusion with the main idea.



However, with the below example, since ‘if’ is used twice, there are two subordinate clauses that can stand alone and must be separated with commas.


Good Luck!

Punctuation can be difficult to get a handle on, but these three areas often cover the majority of confusion with commas. More specific rules can vary depending on which style guide you use, so be sure to default to the guidelines provided in those.




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