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: All chemical reactions require activation energy to get started. 
Sentence2: Catalysts lower the activation energy.
[A]: activation


[Q]: Sentence1: Cells are programmed to divide only a set number of times. 
Sentence2: Cells reproduce asexually, by dividing.
[A]: divide


[Q]: Sentence1: when the seasons change from the summer to the fall , the amount of daylight will decrease. 
Sentence2: Seasons are caused by the Earth's distance from the Sun changing.
[A]:
seasons