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: creating paper requires cutting down trees. 
Sentence2: Trees begin as epiphytes on host trees.
Example Output: trees

Example Input: Sentence1: Osteoporosis is a disease in which osteoclasts are more active than osteoblasts. 
Sentence2: a thinning and weakening of bone is a disease in which osteoclasts are more active than osteoblasts.
Example Output: active

Example Input: Sentence1: Animals are a kingdom of multicellular eukaryotes. 
Sentence2: All plants are eukaryotes.
Example Output:
eukaryotes