For example is NASA simply "NASA" or "a NASA" or "o NASA"?

What rule(s) determine the answer? The gender of the principal word in the acronym ("agency"/"agência" in this example)? The natural gender of the "word" (e.g. "nasa" would appear feminine), or something else?


3 Answers 3


Yes, they do. Its gender is determined by the main noun.


  • NASA is an agency (agência, f.) → a NASA
  • RAM is a memory (memória, f.) → a RAM
  • NATO is an organization (organização, f.) → a NATO or a OTAN (Organização do Tratado do Atlântico Norte)
  • IMF is a fund (fundo, m.) → o IMF or o FMI (Fundo Monetário Internacional)
  • TGV is a train (comboio, m. / trem, m.) → o TGV (Train à grande vitesse)


  • Sometimes the noun is implicit as in "the MI5 (Service)" → o (Serviço) MI5.
  • The same rule applies to Portuguese acronyms like o IST, which stands for Instituto Superior Técnico, where instituto is a masculine noun.
  • 1
    We talk "a OTAN" :)
    – Maniero
    Jul 15, 2015 at 1:08
  • 1
    @bigown I've edited the answer. Jul 15, 2015 at 6:36
  • 1
    @bigown In Portugal we use NATO more, but OTAN is also used.
    – ANeves
    Jul 15, 2015 at 10:34
  • Your answer is solid, but it does not address cases such as "o FBI" (a Agência Federal de Investigação), as @someonewithapc raised in his question.
    – ANeves
    Jul 15, 2015 at 10:51
  • 3
    @ANeves "o FBI" é sem dúvida uma agência, mas na sigla o substantivo principal é "bureau", no sentido de "departamento (governamental)", daí o artigo definido masculino; por oposição "a CIA", cujo substantivo é "agency". Jul 15, 2015 at 14:19

Yes, they do. Generaly the same rules used to determine the gender of a word in Portuguese are applied; an example of these rules is checking wheter the word ends in a or in o. For instance, it seems natural to me to say a NASA, a NSA, but not a FBI and rather o FBI.

However, there are no fixed rules on which to use, so you'll just use which ever sounds better.


Acronyms are written just like they were written in words.

Os Estados Unidos da America. Os EUA.

O Reino Unido. O RU.

Foreign acronyms are no different, the only problem is determining the gender of the foreign word.

Most times it takes the gender of the most common Portuguese translation.

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