の一つだ

One of

Level 2Sounds Like nohitotsuda

[Noun A] は [Category Noun B] + の一つだ
Meaning: "[A] is one of [B]."
Used to categorize a specific thing within a broader group.

How It Works

The structure の一つだ is a fundamental way to express categorization in Japanese. It is composed of the possessive particle の, the counter 一つ, and the copula だ.

Key Usage Points:

  • Category Requirement: The noun preceding 'の一つ' must represent a group, category, or plural concept (e.g., 'cities', 'problems', 'reasons').
  • People vs. Objects: This pattern is used for inanimate objects and abstract concepts. When referring to one person within a group, you must use の一人（ひとり）だ instead of の一つだ.
  • Superlatives: It is very frequently paired with superlatives like 一番（いちばん） or 最も（もっとも） to mirror the English 'one of the most...' structure (e.g., 'one of the most famous cities').
  • Register: It is widely used in both speech and writing. In formal or literary contexts, it often appears as の一つである.
  • Abstract Concepts: Unlike the basic use of '一つ' for physical objects, this pattern is frequently used for abstract ideas like 'one of the reasons'（理由の一つ） or 'one of the challenges'（課題の一つ）.
  • Historical Context: This pattern became popular during the Meiji era as a direct translation of the English 'one of...' structure, though it is now completely natural in modern Japanese.

Examples (4)

  1. 京都は日本の最も美しい都市の一つだ。

    Kyoto is one of Japan's most beautiful cities.

    Word by Word: Kyoto (topic) Japan's most beautiful cities' one is.

    Here, 'cities' (都市) is the category, and Kyoto is identified as one member of that group.

  2. この問題は、現代社会が直面している大きな課題の一つです。

    This problem is one of the major challenges facing modern society.

    Word by Word: This problem (topic), modern society (subject) is facing big challenge's one is.

    This shows the pattern used with an abstract noun 'challenge' (課題) in a polite sentence using です.

  3. 彼が会社を辞めた理由は一つではないが、残業の多さもその一つだ。

    There isn't just one reason he quit, but the amount of overtime is one of them.

    Word by Word: He (subject) company (object) quit reason (topic) one is not but, overtime's amount also that one is.

    In this case, 'that one' (その一つ) refers back to the previously mentioned category of 'reasons'.

  4. 富士山は日本のシンボルの一つとして知られている。

    Mount Fuji is known as one of the symbols of Japan.

    Word by Word: Mount Fuji (topic) Japan's symbol's one as is known.

    This combines the pattern with として (as) to show the subject's role as a member of a group.

Common Mistakes

  • Using 一つ for people.

    彼は私の親友の一つだ。
    彼は私の親友の一人だ。

    When referring to people, you must use the counter 一人（ひとり） instead of 一つ（ひとつ）.

  • Omitting the particle の.

    これは有名な都市一つだ。
    これは有名な都市の一つだ。

    The particle の is required to link the category noun to the word 'one'（一つ）.

How It Connects

Tap a pattern to see what it builds on and what it leads to.

の一つだLevel 2One of

Learn This First

To understand 'の一つだ', you need to know how to use the particle 'の' to show possession or belonging, the general counter 'つ' for counting objects, and the basic copula 'だ' to state that something 'is' a certain way.

Words in This Pattern