1.
Therein means contained in the place that has been mentioned. (FORMAL)
By burning tree branches, pine needles, and pine cones, many not only warm their houses but improve the smell ~.
ADV: n ADV
2.
Therein means relating to something that has just been mentioned. (FORMAL)
Afternoon groups relate to the specific addictions and problems ~.
ADV: n ADV
3.
When you say ~ lies a situation or problem, you mean that an existing situation has caused that situation or problem. (FORMAL or OLD-FASHIONED)
Santa Maria di Castellabate is barely mentioned in guidebooks; ~ lies its charm.
PHRASE: V inflects, PHR n