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 Input:
Sentence1: Mating is generally preceded by courtship. 
Sentence2: Mating is generally similar across species.

Ex Output:
Mating


Ex Input:
Sentence1: the ovaries are used in reproduction. 
Sentence2: Egg released by the ovary.

Ex Output:
ovaries


Ex Input:
Sentence1: condensing causes a liquid to form. 
Sentence2: Condensing is a gas turning into a liquid.

Ex Output:

liquid