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: mineral graphite is used for making pencil lead. 
Sentence2: Diamond and graphite are made of carbon.
[A]: graphite


[Q]: Sentence1: a wildfire changes an ecosystem drastically. 
Sentence2: Forest fires change an ecosystem drastically.
[A]: changes


[Q]: Sentence1: Migrant birds arrive. 
Sentence2: birds travel long distances.
[A]:
birds