Adverbs with Suru & Naru

We already know how to change an adjective to an adverb and connect it to a verb to describe how an action is performed.

仕事しごとが早はやく終おわった。

My work finished early.

明確めいかくに説明せつめいする。

To explain clearly.

However, there are two specific verbs that require special attention when paired with these adverbial forms: the verbs “to do” (する) and “to become” (なる). When combined with adjectives and nouns, they create the essential phrases “to make [something] X” and “to become X”.

The Conjugation Rules

Before looking at the verbs, here is the formula for preparing your adjectives and nouns:

• i-Adjectives: Drop the い and add く (e.g., 安やすい → 安やすく)
• na-Adjectives: Drop the な and add に (e.g., きれいな → きれいに)
• Nouns: Simply add に (e.g., 医者いしゃ → 医者いしゃに)

Adverb + する (To Make…)

On its own, する means “to do”. We cannot use it directly with an object noun like a book (本ほんをする – “To do a book” makes no sense). However, if we insert an adjective in its adverbial form, the meaning of する transforms from “to do” into “to make” or “to change the state of”.

Because you are actively changing something, this is a transitive action. You must mark the thing you are changing with the object particle を.

本ほんを安やすくする。

To make the book cheap (to lower the price).

部屋へやをきれいにする。

To make the room clean (to tidy up).

ケーキを半分はんぶんにする。

To make the cake into halves (to cut it in half).

Adverb + なる (To Become…)

Unlike する, which requires human action, なる is an intransitive verb. It describes a natural change of state (“to become”). Because the object is changing on its own, we do not use を. Instead, we mark the subject of the change with the particle が.

本ほんが安やすくなりました。

The book has become cheap (the price went down).

部屋へやがきれいになりました。

The room has become clean.

息子むすこが医者いしゃになりました。

My son became a doctor.

Note: This structure is particularly important because it is used more frequently in Japanese than in English. We don’t typically say “the weather has become good” in English, but in Japanese, 天気てんきがよくなりました is the most natural way to express that the weather has improved.

Side-by-Side Comparison

To master this grammar point, pay close attention to the difference in particles between the two verbs:

テレビを安やすくする。

I will make the TV cheaper. (Active choice / Transitive)

テレビが安やすくなる。

The TV will become cheaper. (Natural change / Intransitive)