here与herein的区别与具体用法？

区别：据21世纪英汉词典，herein为"副词，(文语)于此,在此中,据此看来",看英文解释：“(formal or law) in this place, document, statement or fact”。here也有“在此处”的意思，但意思为“in, at or to this position or place”，强调的位置。所以，herein用法更为正式，在文中可以作为上下文语境的"在此处"讲。而here指的是物理性"位置",即"position or place”。经查阅权威资料，自己总结，全网搜索并无其他人给出过好的答案。相信自己的解释为正确的。
具体用法嘛，那就是副词嘛，副词咋用你就咋用是了，并不难。
另附英语学习的一点心得：对于这种相近词的辨析，记住去看它的英文解释，不要单单看汉语注释，会对你的理解很有帮助。

It is correct to say "in here" when you enter a room or building, somewhere inside.

It's cold in here.
It's dark in there.
It's pretty in here.
He in there. (pointing to the door of a room)

By just using the word "here", you can be talking about a general location, not usually inside but it could be inside.
Wow! It's cold here. (in Alaska)
Why are you here? (why are you present?)
Why are you in here? (why aren't you outside?)

Normally when we are specifically talking about the interior location of something or someone, we say "in here".

I hope this helps.