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: Ions are atoms or groups of atoms that carry a positive or negative electrical charge. 
Sentence2: An ion is formed after a neutral atom loses an electron.

A: Ions
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Q: Sentence1: burning fossil fuels increases the carbon in the atmosphere. 
Sentence2: the byproduct of fossil fuels is carbon.

A: carbon
****
Q: Sentence1: dropping an object into water causes vibrations in the water. 
Sentence2: Sound vibrations can be compared to pond ripples.

A:
vibrations
****