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


[Q]: Sentence1: Amphibians have permeable skin that easily absorbs substances from the environment. 
Sentence2: permeable skin easily absorbs air to breathe through.
[A]: absorbs


[Q]: Sentence1: Air pressure is a measure of the weight of the air. 
Sentence2: A barometer is used to measure the weight of the air.
[A]:
air