有这么几个名词：英格兰、苏格兰、爱尔兰、北爱尔兰、英国、大不列颠、大不列颠及北爱尔兰联合王国。中国人认为“大不列颠及北爱尔兰联合王国”是英国的全程，它有四个部分组成。这是中国人的印象。但我在和英国朋友交流过程中，发现他们不喜欢用“英国”来概括自己从哪儿来，更喜欢用“英格兰”等来称呼自己来自哪儿。

We use 英国 to mean Britain, and 英格兰 to mean England. As far as I know, Britain means exactly the same thing as the United Kingdom, which is made up of Great Britain and Northern Ireland, while Great Britain, which we call 大不列颠 in Chinese, only comprises England, Scotland and Wales. On formal occasions, it is possible to use 大不列颠及北爱尔兰联合王国, for instance, 中华人民共和国与大不列颠及北爱尔兰联合王国关于香港问题的联合声明.

"England (英国)"。This is absolutely wrong. 英国 means and only means the UK, not England, not Britain. England is and is only called 英格兰。

yes, how to distinguise them correctly?

England (英国), Britain (不列颠/ 大不列颠) and the United Kingdom 联合王国. For most Chinese, they have the same meaning. BUT, those who had been middle school with geographical course should remember that they are different. In recent years, more people in China, especially who went to high school, realise that English is just an country. Lastly, as for English Majors should clearly know the differences between these three.