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.

Sentence1: Mad Cow disease is a concern. 
Sentence2: pathogens can cause Mad Cow.
Cow

Sentence1: Sex hormones are chemical messengers that control sexual development and reproduction. 
Sentence2: Androgens are male sex hormones.
Sex

Sentence1: If a planet is too close to a star, then it will be too hot for liquid water to exist. 
Sentence2: If a planet is too close to a star, that planet cannot sustain life.

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