You already know the ない form (食べない, 行かない) -- it works perfectly for everyday speech. But open a novel, watch the news, or read a JLPT reading passage, and you'll constantly encounter another negative form -- ず.
今日は一日中何もせずに家でゆっくり休んでいた。 → I didn't do anything all day and just relaxed at home.
What's this「せずに」? It's simply the written/formal version of「しないで」.
ず = The Literary ない
ず is a negative auxiliary verb carried over from classical Japanese. In modern Japanese, ず = ない, just with a more formal, literary tone.
| ない form | ず form |
|---|---|
| 食べない | 食べず |
| 行かない | 行かず |
| 読まない | 読まず |
| 飲まない | 飲まず |
| しない | せず |
| 来ない (こない) | 来ず (こず) |
Conjugation Rule
ず attaches the same way as ない: verb negative stem (未然形) + ず.
Simply put: replace ない with ず.
But there are two irregular forms to memorize:
| Verb | ない form | ず form | Note |
|---|---|---|---|
| する | しない | せず | Not しず |
| 来る | こない | こず | Same stem as ない |
ずに = ないで
ず plus に becomes ずに, which functions exactly like ないで -- meaning "without doing something."
-
朝ご飯を食べずに学校に行った。 → I went to school without eating breakfast. (= 食べないで)
-
辞書を使わずに読んでみてください。 → Please try reading it without using a dictionary. (= 使わないで)
-
何もせずにぼーっとしていた。 → I just spaced out without doing anything. (= しないで)
-
誰にも言わずに出かけた。 → I left without telling anyone. (= 言わないで)
ずに and ないで are interchangeable. ずに is more formal and suited to written language.
ず Used Alone: Mid-Sentence Pause
Besides appearing as ずに, ず can stand alone in the middle of a sentence as a pause (similar to the conjunctive use of なくて).
-
雨がやまず、試合は中止になった。 → The rain didn't stop, and the match was canceled.
-
理由が分からず、困っている。 → I don't know the reason, so I'm at a loss.
ず used alone mid-sentence = similar to なくて for expressing cause or listing.
Common Set Phrases
ず appears in many fixed expressions and idioms, frequently used even in spoken language:
| Expression | Meaning | Example |
|---|---|---|
| 知らず知らず（のうちに） | Without realizing, unconsciously | 知らず知らずのうちに寝ていた。(I fell asleep without realizing it.) |
| 思わず | Involuntarily, reflexively | 思わず笑ってしまった。(I couldn't help but laugh.) |
| 絶えず | Constantly, unceasingly | 絶えず努力している。(I'm constantly making an effort.) |
| 限らず | Not limited to | 男女を問わず、年齢を問わず。(Regardless of gender or age.) |
These have become fixed as adverbs or set phrases -- just memorize them as units.
ず vs ない: When to Use Which?
| Context | Use ない | Use ず |
|---|---|---|
| Everyday conversation | ○ | △ (too formal) |
| Writing / essays | ○ | ○ |
| News / reports | △ | ○ |
| Novels / literature | ○ | ○ |
| Set phrases | -- | ○ (知らず知らず, etc.) |
| N4 exam reading | ○ | ○ (will appear) |
Use ないで in conversation, but instantly recognize ずに as ないで when you see it -- this comes up frequently in exam reading sections.
Self-Test
Q1. Rewrite「何も食べないで出かけた」in literary style.
Show answer
何も食べずに出かけた。 Just replace ないで with ずに.
Q2. What is the ず form of する?
Show answer
せず. する has an irregular change -- it's not しず. The ずに form is せずに.
Q3. What does「知らず知らずのうちに太ってしまった」mean?
Show answer
I gained weight without realizing it. 知らず知らず = without realizing, a fixed ず expression.
Summary
- ず = the literary form of ない, with the same conjugation pattern
- ずに = ないで (without doing something), interchangeable but more formal
- ず used alone mid-sentence = similar to なくて (cause/listing)
- する → せず, 来る → こず (two irregular forms)
- Fixed phrases like 知らず知らず, 思わず, 絶えず should be memorized as units