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: Soil Erosion Soil erosion is a natural process. 
Sentence2: wind and rain is a natural process.
[A]: natural


[Q]: Sentence1: Flies are insects with two wings. 
Sentence2: Flies are arthropods with two wings.
[A]: Flies


[Q]: Sentence1: Mass Amount of matter an object contains. 
Sentence2: phase changes do not change amount of matter.
[A]:
Amount