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

   "they can read therein what our plans are"
   

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

e.g. By burning tree branches, pine needles, and pine cones, many not only warm their houses but improve the smelltherein.
许多人在家里烧树枝、松针和松果，不但给房子取暖，还改善了屋里的气味。

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

e.g. Afternoon groups relate to the specific addictions and problemstherein.
下午的小组谈到具体的上瘾病例以及其中的问题。

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

e.g. Santa Maria di Castellabate is barely mentioned in guidebooks;therein lies its charm.
卡斯特拉巴泰的圣玛丽亚在旅行指南里鲜有被提及，而它的魅力正在于此。

1. 在那里：therefrom 从此 |therein 在那里 |thereinafter 以下

2. 在其中：therefore 所以 |therein 在其中 | thereof 关於

3. 在那里,在那时：therefore 因此,所以 | therefrom 由此 |therein 在那里,在那时

4. 在其中/在那里/在那一点上：therefrom /从此/从中/ |therein /在其中/在那里/在那一点上/ |thereinafter /在下文/以下/