You have my word与I promise you有何区别?

都表示许诺对方。

1、You have my word.用在和别人讨论后的追加确认。较口语化。

2、Promise 用法较为正式，庄重。

1）承诺；保证；答应 If you promise that you will do something, you say to someone that you will definitely do it.

The post office has promised to resume first class mail delivery to the area on Friday.邮局承诺于星期五恢复对这个地区第一类邮件的递送。

He had promised that the rich and privileged would no longer get preferential treatment.他已经保证富人和特权阶层不会再得到优惠待遇。

2）答应给予；承诺给予；保证让…得到 If you promise someone something, you tell them that you will definitely give it to them or make sure that they have it.

In 1920 the great powers promised them an independent state.1920年，列强承诺让他们成为一个独立的国家。

The officers promise a return to multiparty rule.这些官员承诺恢复多党统治。