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: rocks interacting with wind over long periods of time causes weathering.
Sentence2: When a rock undergoes erosion and weathering, it breaks down to form sediments.

A: weathering
****
Q: Sentence1: the ovaries are used in reproduction.
Sentence2: Unlike most female animals, which have two functioning ovaries, the chicken usually has only one.

A: ovaries
****
Q: Sentence1: When a substance melts, it changes phase from a solid to a liquid by the application of heat.
Sentence2: Changing the phase of a solid can be done by adding heat energy.

A:
changes
****