Grammatically speaking, what is もう一つ?

Question

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!

Answer 1

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)
• How to list numbers of things
• たくさんの本を読んで versus 本をたくさん読んで

Answer 2

At my first glance of this question, I thought you are tired. But it turns me out a good question indeed, what is もう in this case?

Adverb もう:

③ すでにある基準や状態に達しているのに、さらに加える意を表す。さらに。 「 －一杯飲もう」 「 －少し右へ寄って」 「 －一度やってみよう」 三省堂　大辞林

The dictionary tells us three more meanings of もう. And in your case the apple was given to the one already and もう is equivalent of additional, frankly say 追加の/追加で

ひとつ can be replaced 一個 in this case, Japanese ひとつ would be many ways to translate into English, e.g. ひと玉のリンゴ、一艘の船、一匹の犬