Over the years, I have had the opportunity to do a lot of copyediting for business professionals. I have seen a lot of great writing, and I have also seen a lot of grammatical mistakes. So today, I am detailing five common mistakes I see in professional writing.

Read on to see if you are making one of these common errors.

Note: I am only referring to American English. 

1.) Writing work place instead of workplace.

This may surprise many of you, but I often see workplace spelled as two words. I especially see this in business-related blogs. So, in case you didn't know, workplace is one word.

2.) Placing the period outside of the closing quotation mark.

This is a pretty confusing one, and I get why. It is common to confuse the period placement in quotation marks for the period placement in parentheses. However, when you are using quotation remarks, the period will always go inside the closing quotation mark.

On the same line of thinking, colons and semi-colons will always go on the outside of quotation marks.

Correct

As Walt Disney said, "The way to get started is to quit talking and begin doing."

Incorrect

As Walt Disney said, "The way to get started is to quit talking and begin doing".

3.) Placing the period inside the parenthesis, when it should be on the outside.

Many don't realize period placement for parentheses changes based on whether or not the parenthetical content is a part of a longer sentence. 

For the record, if the parenthetical content is a part of another sentence, the period will go on the outside of the closing parenthesis. If the parenthetical statement stands alone, then the period goes on the inside of the closing parenthesis. 

Correct

He didn't know whether he liked her or not (which was a common problem with him).

Incorrect

He didn't know whether he liked her or not (which was a common problem with him.)

Correct

(I am not sure what I am supposed to do.)

Incorrect

(I am not sure what I am supposed to do).

4.) Using hyphens instead of an em dash.

Whew! I see this one all the time. I am not even sure many people know there is a difference between a hyphen and a dash.

To clarify their differences, I'll define the two below.

A hyphen is a short line and has five purposes.

1.) To link a compound modifier when the modifier comes before the word it is modifying (e.g., please send a follow-up email)

2.) To create a compound adjective

3.) To indicate the continuation of a word at the end of a line

4.) To link a prefix with the word it is modifying

5.) To show there is a missing element

An em dash (not to be confused with an en dash) is a long line—about the length of an "m"—and also has four purposes.

1.) To use in place of a comma

2.) To use in place of a pair of parentheses

3.) To use in place of a colon mark

4.) To indicate the missing portion of a word (you will need to place two em dashes together to accomplish this purpose)

Now, I realize that many people use a hyphen instead of an em dash because they don't know how to type an em dash. I am going to help you with that. 

To create an em dash, type two hyphens in a row and then your next letter and most word processors will create an em dash for you.

5.) Not putting a comma before a coordinating conjunction in a compound sentence. 

This is the number one mistake I see in professional writing (including my own!). Heck, I'll even find this mistake in published books.

The rule is this: when combining two independent clauses (two simple sentences) with a coordinating conjunction (i.e., but, and, yet, nor, or, etc.), there needs to be a comma before the conjunction.

Correct 

I am not sure where we are going, but I am sure that we will find the location.

Incorrect

I am not sure where we are going but I am sure that we will find the location.

Do you make any of the grammatical mistakes I discussed? Or, if you are also a grammar nerd, which grammar mistake do you see most often?