Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Q: Sentence1: Carpools and vanpools can save time. 
Sentence2: vanpools decrease the amount of cars used to travel to a place.

A: vanpools
****
Q: Sentence1: natural magnetism is used for pointing north by a compass. 
Sentence2: For the ordinary compass, align to the North direction.

A: north
****
Q: Sentence1: planting trees has a positive impact on an ecosystem. 
Sentence2: planting trees has a positive impact on biodiversity.

A:
impact
****