副词

1. 在那里;在其中
Therein means contained in the place that has been mentioned.

2. 其中(指和刚提及的事情有关)
Therein means relating to something that has just been mentioned.

3. 此即，缘此(用以说明某事是由某种情况导致)
When you say therein lies a situation or problem, you mean that an existing situation has caused that situation or problem.

1. (formal) in or into that thing or place

e.g. they can read therein what our plans are

Synonym: in thisin that