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: rain causes erosion. 
Sentence2: Soil Erosion Soil erosion is what happens when soil is washed or blown away.

A: erosion
****
Q: Sentence1: Interstellar space contains a plasma. 
Sentence2: interstellar space contains electrons, atoms, and stars.

A: Interstellar
****
Q: Sentence1: a nest is used for protecting young by birds. 
Sentence2: Nests are used to protect eggs from predators and extreme temperatures.

A:
nest
****