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.

[EX Q]: Sentence1: Echinoderms use pheromones to communicate with each other. 
Sentence2: Echinoderms are known for their round symmetry.
[EX A]: Echinoderms

[EX Q]: Sentence1: ultraviolet light causes sunburn. 
Sentence2: Sunburn risk is higher at elevation.
[EX A]: sunburn

[EX Q]: Sentence1: Earth orbiting the Sun causes seasons to change. 
Sentence2: seasons happen because of orbital tilt.
[EX A]:
seasons