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: People of all ages and activity levels perspire or sweat. 
Sentence2: Perspiration reduces body heat.
[A]: perspire


[Q]: Sentence1: Fertilization is the penetration of the egg by a sperm. 
Sentence2: Sperm must swim from the male to the female egg.
[A]: egg


[Q]: Sentence1: Snakes are cold-blooded reptiles. 
Sentence2: some snakes can go several weeks between meals.
[A]:
Snakes