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: Germination depends on the seed coat. 
Sentence2: the force of water causes germination with the emergence of a root.
Example Output: Germination

Example Input: Sentence1: plant reproduction requires pollination. 
Sentence2: Plant reproduction requires insects and hummingbirds.
Example Output: plant

Example Input: Sentence1: Reptilia contains over 7800 entries on numerous species of reptiles. 
Sentence2: Most animals in the class reptilia have good eyesight and a keen sense of smell.
Example Output:
Reptilia