The Written ないで
ずに means "without doing" and is the formal counterpart of ないで.
- 朝ごはんを食べずに出かけた。(I left without eating breakfast.)
| Register | Form |
|---|---|
| everyday | 食べないで |
| written | 食べずに |
The する Irregularity
Drop ない and add ずに — except for する, which becomes せずに:
| Verb | ない form | ずに form |
|---|---|---|
| 食べる | 食べない | 食べずに |
| 行く | 行かない | 行かずに |
| する | しない | せずに |
| 来る | 来ない | 来ずに |
This is the same irregularity as ずにはいられない, which is built on this form.
Against なくて
なくて is a reason ("because I didn't"); ずに and ないで describe manner ("without doing"):
| 行かずに電話した | I phoned instead of going |
| 行けなくて残念だ | I'm sorry I couldn't go |
ずには and なしに
ずに済む means to get away without doing something. なしに is a near-synonym that attaches to nouns: 連絡なしに来た.