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: nectar is used for attracting pollinators by plants. 
Sentence2: butterflies pollinate plants.
Example Output: plants

Example Input: Sentence1: Ovulation is the release of an egg from an ovary. 
Sentence2: The release of an egg during ovulation is used in reproduction.
Example Output: Ovulation

Example Input: Sentence1: Invertebrates are animals that lack a vertebral column, or backbone. 
Sentence2: Insects are the most common invertebrates.
Example Output:
Invertebrates