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.

Input: Consider Input: Sentence1: Antibiotics and vaccines are being stockpiled as Britain gears up to meet the bioterrorism threat.
Sentence2: Antibiotics and vaccines are being stockpiled against another potential threat in the environment.

Output: Antibiotics

Input: Consider Input: Sentence1: high pressure systems cause clear weather.
Sentence2: Weather Clear weather usually means good visibility.

Output: clear

Input: Consider Input: Sentence1: What semen is, is a carrier for the sperm contained in it.
Sentence2: semen goes from male to female reproductive organs for fertilization.
Output: semen