Rule 1: You should put a comma after a period in an abbreviation when the abbreviation ends an introductory clause.
- Correct: Starting in Nov., we will be advertising for the new role.
- Incorrect: Starting in Nov. we will be advertising for the new role.
Rule 2: Use a comma after the period in an abbreviation when it comes in a list.
- Correct: We need proof of address, D.O.B., and valid identification.
- Incorrect: We need proof of address, D.O.B. and valid identification.
Rule 3: Use a comma after the period in an abbreviation when it comes before a non-defining element in a sentence.
- Correct: I tried to do some D.I.Y., which I have been meaning to do for ages, but I got sidetracked again.
- Incorrect: I tried to do some D.I.Y. which I have been meaning to do for ages, but I got sidetracked again.
Rule 4: Use a comma after the period when the abbreviation comes at the end of a non-defining element.
- Correct: He applied for several jobs, e.g., office manager, marketing assistant, and chef, but he didn’t get any.
- Incorrect: He applied for several jobs, e.g. office manager, marketing assistant, and chef, but he didn’t get any.
Rule 5: Do not use a comma when you use an abbreviation directly before a name.
- Correct: Dear Mrs. Jones,
- Incorrect: Dear Mrs., Jones,
Rule 6: Do not put a comma after the period when the abbreviation forms an essential part of a sentence.
- Correct: You must bring an I.D. if you want to enroll.
- Incorrect: You must bring an I.D., if you want to enroll.
Keep reading to discover more about using commas after periods in abbreviations.
When to Use a Comma After a Period in an Abbreviation
To know when to use a comma after a period in an abbreviation, you should refer to Rules 1-4.
Rule 1: Use a comma after a period in an abbreviation when the abbreviation comes at the end of an introductory clause.
This rule applies to all introductory clauses and is not specific to abbreviations.
- Without an I.D., you cannot access your accounts.
- When he lived in N.Y.C., all his money went on rent.
Rule 2: Use a comma after a period in an abbreviation when it forms part of a list.
For these lists, you should separate all the items with commas.
Just because abbreviations have periods does not exempt them from this rule.
- He has a B.A., M.A., and a Ph.D., which are all in art-related subjects.
- He has lived in L.A., S.F., and N.Y.C., but he didn’t like any of them.
Rule 3: Use a comma after a period in an abbreviation when it appears before a non-essential element.
A non-essential element means that if you remove it, the sentence still makes sense.
You should put a comma when you have an abbreviation just before one of these removable elements.
- He did not complete his B.A., which was not a surprise, and left after just one semester.
- Military personnel going A.W.O.L., which has grown in number, costs the Government millions of dollars annually.
Rule 4: Use a comma after a period in an abbreviation when it comes at the end of a non-essential clause.
You need to enclose these clauses in commas if they are removable.
- We asked him to bring several things, including his I.D., but he didn’t bring any of them.
- Many modern abbreviations, such as EDM. and LOL., have become part of everyday language.
When to Avoid a Comma After a Period in an Abbreviation
Rules 5 and 6 explain when you shouldn’t be using a comma after a period in an abbreviation.
Rule 5: You shouldn’t use a comma after a period in an abbreviation when the abbreviation comes directly before a name or title.
- The Rt Hon. David Clark will be chairing the conference this afternoon.
- Mr. Ronald Pickering will be your lecturer for this semester.
Rule 6: You shouldn’t use a comma after a period in an abbreviation when it forms an essential part of a sentence.
That means that if you cannot remove the clause that contains the abbreviation, you should not use a comma after it.
- Apple Computers changed its name to Apple Inc. in 2007.
- B.A. is one of the oldest airlines in the world and is still operating today.
Conclusion
Put a comma after the period in an abbreviation when you use them in a list. Also, you should put a comma when it appears before or within a non-essential clause. Likewise, do not put a comma when a name follows the abbreviation or when it is essential for the sentence’s meaning.