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.

Example Input: Sentence1: Fertilization occurs naturally in the fallopian tubes. 
Sentence2: fertilization is used for reproduction.
Example Output: Fertilization

Example Input: Sentence1: if an organism becomes too hot then that organism may die. 
Sentence2: a plant can collapse if it gets too hot.
Example Output: hot

Example Input: Sentence1: Many plants are in a dormant state in winter. 
Sentence2: some plants are dormant when the days are shorter.
Example Output:
dormant