Grammatically speaking, what is もう一つ?


I have come across `もう一つ` multiple times now, and I know it means "another
one", but I'm struggling to understand it's grammatical function in a
sentence.

It looks like the combination of the adverb `もう` and the counter `一つ`, so is
it a compound phrase or an independent word?

I've seen it modify nouns (e.g. `もう一つリンゴ`, "another apple"), kind of like an
adjective.

I've also seen it in other positions in a sentence (e.g. `リンゴをもう一ついかがですか。`,
"Would you like another apple?"). In this case, it seems to modify the
sentence predicate.

I guess my question is, grammatically speaking, what is `もう一つ`? I haven't been
able to find enough information/clarification in my studies.

Thank you very much for your help!




もう is an **adverb** as you suspected, and it is modifying ひとつ. ひとつ works
either as a **no-adjective** , as a **pronoun** , or as an **adverb**.
(Adverbs can modify another adverb/adjective, right? For example, "very well"
as in "He plays tennis very well" is a combination of two adverbs, and "very
good" is an adverb-adjective pair.)

もうひとつ as a whole works as a no-adjective:

> このリンゴは黄色くて、 **もうひとつの** リンゴは赤い。  
>  This apple is yellow and the other apple is red.

...or as an adverb:

> **もうひとつ** リンゴを食べた。  
>  リンゴを **もうひとつ** 食べた。  
>  I ate another apple.

...or as a pronoun meaning "another (one)" or "the other (one)":

> ひとつは青くて、 **もうひとつ** は赤い。  
>  One is blue and the other is red.

(An adverb normally doesn't modify a (pro)noun, but I think this use is an
exception...I think you can say " _Yet_ another is ..." in English, too.)

Note that もうひとつリンゴ is _ungrammatical_ if presented in isolation like this. If
you want to say "another apple" as a noun phrase, you have to say もうひとつ **の**
リンゴ, in which case ひとつ is a no-adjective. もうひとつリンゴを食べる is grammatical, but in
this case もうひとつ is modifying 食べる, not リンゴ.

In general, counters (as well as similar words related to quantity) in
Japanese work both as adverbs and no-adjectives. This has been asked many
times, so please read the following questions.

  * [Positioning of quantities (using counters)](https://japanese.stackexchange.com/q/8136/5010)
  * [How to list numbers of things](https://japanese.stackexchange.com/q/17816/5010)
  * [たくさんの本を読んで versus 本をたくさん読んで](https://japanese.stackexchange.com/q/27483/5010)




もう is an **adverb** as you suspected, and it is modifying ひとつ. ひとつ works
either as a **no-adjective** , as a **pronoun** , or as an **adverb**.
(Adverbs can modify another adverb/adjective, right? For example, "very well"
as in "He plays tennis very well" is a combination of two adverbs, and "very
good" is an adverb-adjective pair.)

もうひとつ as a whole works as a no-adjective:

> このリンゴは黄色くて、 **もうひとつの** リンゴは赤い。  
>  This apple is yellow and the other apple is red.

...or as an adverb:

> **もうひとつ** リンゴを食べた。  
>  リンゴを **もうひとつ** 食べた。  
>  I ate another apple.

...or as a pronoun meaning "another (one)" or "the other (one)":

> ひとつは青くて、 **もうひとつ** は赤い。  
>  One is blue and the other is red.

(An adverb normally doesn't modify a (pro)noun, but I think this use is an
exception...I think you can say " _Yet_ another is ..." in English, too.)

Note that もうひとつリンゴ is _ungrammatical_ if presented in isolation like this. If
you want to say "another apple" as a noun phrase, you have to say もうひとつ **の**
リンゴ, in which case ひとつ is a no-adjective. もうひとつリンゴを食べる is grammatical, but in
this case もうひとつ is modifying 食べる, not リンゴ.

In general, counters (as well as similar words related to quantity) in
Japanese work both as adverbs and no-adjectives. This has been asked many
times, so please read the following questions.

  * [Positioning of quantities (using counters)](https://japanese.stackexchange.com/q/8136/5010)
  * [How to list numbers of things](https://japanese.stackexchange.com/q/17816/5010)
  * [たくさんの本を読んで versus 本をたくさん読んで](https://japanese.stackexchange.com/q/27483/5010)

