Consider the following two sentences, dealing with a singular "ISP":

(1) The virus penetrated the Internet Service Provider's (ISP)'s firewall.


(2) The virus penetrated the Internet Service Provider (ISP)'s firewall.

The subtle difference is that (1) has a possessive apostrophe both on the term and its abbreviation, whereas (2) only has it on the abbreviation. Which of the above two is more commonly preferred?

  • 1
    They're both bad. You should recast the sentence so that "Internet Service Provider" doesn't need a possessive, or define the abbreviation earlier in your text and just use "... the ISP's firewall" here.
    – Hellion
    Commented Jan 15, 2015 at 20:22
  • "The virus penetrated the firewall of the Internet Service Provider (ISP)." Solved.
    – David
    Commented Jul 7, 2017 at 12:52

2 Answers 2


If you can't rephrase, then:

... the Internet Service Provider's (ISP) firewall.

The abbreviation is included in the sentence, rather artificially, solely to inform the reader of it, so make that the sole job it does.

By the same token, if you took the opposite approach to defining abbreviations on first use:

... the ISP's (Internet Service Provider) firewall.

But, rephrased is likely better.


Technically, you don't need the possessive apostrophe on the abbreviation at all. It's an abbreviation; only the first letters in each word are represented.

Not the answer you're looking for? Browse other questions tagged or ask your own question.