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.

Sentence1: Soil Erosion Soil erosion is a natural process. 
Sentence2: wind and rain is a natural process.
natural

Sentence1: Polyps usually reproduce asexually. 
Sentence2: Polyps usually reproduce several different ways.
Polyps

Sentence1: Mollusks are a major food source for other organisms, including humans. 
Sentence2: Invertebrates are a major food source for other organisms, including humans.

food