Assume that TSFI stands for TOE Security Function Interface. And TOE (The first word) stands for Target Of Evaluation.

I want to know in the TSFIs the plural s returns to which word(s)?

  • 2
    TSFIs should be expanded to either TOE Security Function Interfaces or Target of Evaluation Security Function Interfaces. It's almost always the case for a long noun phrase that the main noun (also known as the head word) is the last word in the phrase. Sep 14, 2014 at 12:50
  • 5
    It is very common for the head noun to be the final word in a noun phrase, but "almost always" is too strong. Many nouns take complements as postmodifiers (RFCs = Requests for Comment), and there are a variety of other postmodifiers, for example relative clauses, which can follow the head noun.
    – user230
    Sep 14, 2014 at 13:00
  • 1
    Technically, RFCs = Requests for Comments (with an 's' at the end), but it's too late to edit my old comment and that makes the example less suitable than I'd like. Here's a less ambiguous example: AGs = Attorneys General.
    – user230
    Sep 14, 2014 at 13:21
  • 1
    There are also some abbreviations where you can't pluralize the expanded form by pluralizing to one of the words. For example, people use POWs and MIAs. This would probably be expanded to "prisoners of war and servicemen missing in action". You certainly wouldn't use "missing in actions" or "missings in action". Sep 14, 2014 at 14:08

1 Answer 1


The rule in expanding acronyms for pluralization, or in pluralizing any noun phrase, is to first figure out what the noun is. It's not always the last word!

In the "TSFIs" example, everything up to "interfaces" is a modifier of what kind of interface it is, therefore "interface" is the noun to be pluralized.

In the "RFCs" example "for Comments" is a modifier of "Request", so "request" is the noun to be pluralized.

In the "Attorneys General" example, "attorney" is the noun being modified by "general", so it's the noun to be pluralized.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .