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: Ovulation is the release of an egg from an ovary. 
Sentence2: The release of an egg during ovulation is used in reproduction.

Ex Output:
Ovulation


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

Ex Output:
Mating


Ex Input:
Sentence1: Many consumers feed at more than one trophic level. 
Sentence2: Many insects and animals feed at more than one trophic level.

Ex Output:

Many