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: sharpening an object causes that object to change shape.
Sentence2: sharpening a knife causes it to change shape.
causes

Sentence1: Mangoes are propagated vegetatively and by seeds.
Sentence2: animals propagate mangoes.
Mangoes

Sentence1: Mutualism is a symbiotic relationship in which both species benefit.
Sentence2: Mutualism is an association between two different species which benefits each species.
Mutualism