Why do we say in English things like a Facebook post, an AWS service, the Silicon Valley, etc.?

In Portuguese, we would say "A post of Facebook", "a service of AWS", and "the Valey of Silicon". It seems to me that Facebook, AWS, Silicon are kind of adjectives in these cases, but in Portuguese, they seem to have more like a relationship of possession.

Is there any grammatical term for this situation?

  • 1
    One good example I came across (as an English speaker learning Spanish) would be "orange juice" vs. "juice of orange". Interestingly, you do see the latter form in some fantasy books and games, with things like "potion of strength" or "curse of binding". Nov 6 '20 at 23:40
  • @RedwolfPrograms "potion of strength" is exactly the kind of literary meaning that I alluded to in my answer.
    – JavaLatte
    Nov 7 '20 at 7:42
  • Note that you can generally say "x of y" in English (in the sense that it is grammatically correct), just as you do in Portuguese, but it sounds awkward to a native English speaker and you should try to avoid it in cases where a compound noun is more idiomatic.
    – Cody Gray
    Nov 7 '20 at 11:15
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    "Silicon Valley" is different from the others because that's a proper noun. A proper noun is a fixed entity and you can't apply language rules to it that might allow you to otherwise have changed the order of the words.
    – NotThatGuy
    Nov 7 '20 at 13:13
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    I would rather say "a post on Facebook". This can sound fine in some contexts, e.g. "I saw a post on Facebook that said ...". If you use "of", this would typically imply the post belongs to or was created by Facebook. That might sometimes work, but "by" might generally be better if you want to imply that.
    – NotThatGuy
    Nov 7 '20 at 17:49

In English, this type of construction is called a compound noun: it is used to describe a specific type of something. The final noun is the general thing, and any nouns in front of it (yes, there can be more than one) specify exactly what kind of thing it is.

As an example, a can is a noun, an opener is a noun, and we can put these two nouns together to form a compound noun- a can opener. Opener is the general noun, and can specifies exactly which kind of opener we are talking about.

We can take this one step further: if we have a special kind of can opener that is used to open paint cans, it would be a paint can opener.

In Portuguese, you describe the opener as a possession of the can... "abridor de lata". Clearly, abridor is not a possession of lata, but in the grammar of Portuguese, that is how you use a noun to specify the exact type of another noun.

It is possible to use the same construction in English, however it is uncommon and perhaps has literary overtones- for example, you could say "a user of drugs" rather than "a drug user".

In some situations, the meaning or emphasis of the of-form is different: a water bottle (compound noun) is a bottle whose specific purpose is to contain water. A bottle of water is some water that is contained in a bottle.

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    You mention "any nouns" in your answer, but I think it's useful to explicitly state that these compound nouns can be stacked up in constructions of more than two nouns. A "cat food can opener" is an opener of cans of food for cats. Nov 6 '20 at 13:44
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    For the latter construction, the preposition could change the meaning. Water bottle is a bottle that can hold water. Bottle of water is a bottle and the water in it. (Closer would be bottle for water.) Using the compound noun is the more reliable way to subclass a general noun. Nov 7 '20 at 5:21
  • @CanadianYankee, PaulDraper, thank you for your comments. I have updated my answer.
    – JavaLatte
    Nov 7 '20 at 7:41
  • @CanadianYankee and indeed "aluminium soup pot lid clearance sale" is grammatical even if semantically unlikely.
    – mdewey
    Nov 7 '20 at 13:32

In English it is possible to use a noun as an adjective

Here is an internet article about this:

As you know, a noun is a person, place or thing, and an adjective is a word that describes a noun ... Sometimes we use a noun to describe another noun. In that case, the first noun "acts as" an adjective ... The "noun as adjective" always comes first



I just discovered today that in Portuguese we use "of", which is "de" in Portuguese, because we are expressing a restrictive adnominal adjunct, or "adjunto adnominal restritivo" in Portuguese, and this is our way of expressing this.

By the way, in Latin it would be the genitive case, so, I would say that this is just how the genitive case is used in both languages.


I would agree with your assessment, that these are adjectival. If something is posted on Facebook then it’s a Facebook post.

Also, if someone said to me, “post of Facebook”, besides sounding slightly odd, I might wonder if they meant that it was Facebook themselves, the company, that did the posting.

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