ないでWithout doing, Not ~ and ~

〜てください is a polite way to say 'Please do (something),' as in 食べてください ('Please eat'). Its negative form, 〜ないで, means 'Don't do (something),' as in 食べないで ('Don't eat'). To make this negative request polite, simply add ください, as in 食べないでください means 'Please don't eat.'

なさい is a firm but polite command form, often used by those in authority (like teachers or parents) toward subordinates. In contrast, ないで is a casual way to ask someone not to do something, e.g. 行かないで ('Don't go.'). It is typically used among close friends or family.

ないでください is a polite way to ask someone not to do something. The shorter form, ないで, is more casual and typically used with close friends or family. While ないでください is appropriate for strangers or people of equal status, ないで has a softer, more informal tone. Adding the sentence-ending particle ね (e.g. 食べないでね) makes the request even gentler and more caring.

ないで and なくて are both connecting forms of ない, but with different uses. ないで is used in negative requests or to mean 'without doing' something, e.g. 食べないでください ('Please don't eat it.') and 朝ご飯を食べないで学校に行った ('I went to school without eating breakfast.'). なくて can express a reason or cause, e.g. 行けなくて残念でした ('I couldn't go, which was disappointing.').

ないで and ずに both express the idea of 'without doing (A)' and are used in similar ways. For example, 朝ご飯を食べないで学校に行った and 朝ご飯を食べずに学校に行った both mean 'I went to school without eating breakfast.', but ずに has a slightly more formal or literary tone, while ないで is more conversational. Unlike ないで, ずに cannot be used as a negative request form to say 'Don't (A).'.

ないで and なくて are both negative connecting forms, but with different uses. ないで is used in negative requests or to mean 'without doing' something, e.g. 食べないでください ('Please don't eat it.'). and 朝ご飯を食べないで学校に行った ('I went to school without eating breakfast.'). なくて connects clauses to describe reasons or states, similar to 'and', e.g. 高くなくて便利です ('It's not expensive, and it's convenient.').

The dictionary/non-past form of a verb + な expresses a blunt command not to do something. Similarly, ないで attached to the negative stem of a verb is a more casual and gentle request. For example, するな is a strong way of saying 'Don't do it!' while しないで is a softer, more casual way of saying '[Please] don't do it.'

The ないで form combines a verb in the negative with で, and has two common uses: (1) to make a negative request, e.g. 食べないで ('Don't eat it.'), and (2) to express 'without doing' something, e.g. 晩ご飯を食べないで出かけた ('I went out without eating dinner.').