日: 2026年5月9日

At the Renshuu A4 in the section 19 of “Minna no Nihongo”, three sentence constructions are introduced. These three are to express changes using the intransitive verb “Naru/Narimasu” as shown below;

1. [Subject] wa [Condition/Nature after the change] Narimashita.

There is [Condition/Nature after the change] in the sentence 1. And for this part, I-adjectives, Na-adjectives, and Nouns can be used.

1-1. [Subject] wa [I-adj]+ku Narimashita.

1-2. [Subject] wa [Na-adj]+ni Narimashita.

1-3. [Subject] wa [Noun]+ni Narimashita.

Though the A4 introduces these three at once, let me explain one by one for the three. Today’s post focuses on sentences of changes of condition/nature described by I-adjectives (1-1).

The first thing you need to accept about Japanese adjectives is that I-adjectives and Na-adjectives do conjugate. And I-adjectives and Na-adjectives conjugate differently. But unfortunately, many Japanese learners do not accept conjugation especially of I-adjectives. Probably this problem is affected by a Na-adjective “Kireina”. So, let us carefully examine conjugation of I-adjectives.

Conjugating words in Japanese are verbs, I-adjectives, Na-adjectives, and Auxiliary verbs. How changes happen are common to these four words groups.

[Conjugating Word] => [Stem]+<Ending> = [Unchanging]+<Changing>

In the case of I-adjectives “Samui (cold)”, the word endings change as below;

<1> Concise ending; [Samu]<i>

<2> Modifying a noun behind; [Samu]<i> Heya (a cold room)

<3> Being connected to another conjugating word behind; [Samu]<ku> narimashita. (It’s become cold.)

<4> To make the adjective hypothetical; [Samu]<kereba> (If it’s cold)

So, you can see that conjugation happens depending on how the conjugating word works in a sentence. And it is important for Japanese learners in beginner’s level to choose properly <2> or <3>;

<2> [I-adj stem]<i> + [Noun] ; Atsui Natsu (Hot summer)

<3> [I-adj stem]<ku> + [Verb/I-adj/Na-adj] ; Atsuku Narimasu (become hot)

“Naru/Narimasu” is not the only verb that follows an I-adjective and make it “stem+ku”. For example;

– Hayaku Hashirimasu. (runs fast)

But “stem+ku Narimasu” is the most major combination of “ku+conjugating words” for I-adjectives. Read aloud the following examples.

– Atarashii Omise (new store) — <2>

  Omise ga Atarashiku Narimashita. — <3>

– Ii Tenki (good weather) — <2>

  Tenki ga Yoku Narimashita. — <3>

– Isogashii Shigoto (busy job) — <2>

  Shigoto ga Isogashiku Narimashita. — <3>

– Oishii Misoshiru (taste-good Miso soup) — <2>

  Misoshiru ga Oishiku Narimashita. — <3>

– O’okii Karada (large body) — <2>

  Karada ga O’okiku Narimashita. — <3>

– Omoshiroi Jugyou (interesting class) — <2>

  Jugyou ga Omoshiroku Narimashita. — <3>

– Takai Se (tall body-height) — <2>

  Se ga Takaku Narimashita. — <3>

– Chiisai Keshigomu (small eraser) — <2>

  Keshigomu ga Chiisaku Narimashita. — <3>

– Tsumetai Kaze (chilly wind) — <2>

  Kaze ga Tsumetaku Narimashita. — <3>

– Hikui ten (low score (of a test)) — <2>

  Tesuto no ten ga Hikuku Narimashita. — <3>

– Furui Ie (old house) — <2>

  Ie ga Furuku Narimashita. — <3>

– Muzukashii Tesuto (difficult test) — <2>

  Tesuto ga Musukashiku Narimashita. — <3>

– Yasashii Shiken (easy examination) — <2>

  Shiken ga Yasashiku Narimashita. — <3>

– Yasui Nedan (cheap price) — <2>

  Nedan ga Yasuku Narimashita. — <3>

Learn when “i” remains “i”, or when “i” needs to be “ku”, for I-adjectives.

This post was written with reference to the exercise A4 on Section 19 of “Minna no Nihongo (2^nd Edition)” published by “3A Corporation”