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

A: Ovulation
****
Q: Sentence1: skin is used for protecting the body from harmful substances. 
Sentence2: Acids are harmful to tissue.

A: harmful
****
Q: Sentence1: Cells are organized into tissues, and tissues form organs. 
Sentence2: Major organs, including the kidneys and liver, begin to grow.

A:
organs
****