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: poisonous darts are used for defense by sea anemones. 
Sentence2: poisonous darts are used for protection by sea anemones.
Example Output: anemones

Example Input: Sentence1: Autumn or Fall is almost over. 
Sentence2: when the seasons change from summer to autumn, the amount of daylight will decrease.
Example Output:
Autumn