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: Flies are insects with two wings. 
Sentence2: Flies are arthropods with two wings.
Example Output: Flies

Example Input: Sentence1: Mammalian predators include the coyote and bobcat. 
Sentence2: a coyote's teeth is important for digestion.
Example Output: coyote

Example Input: Sentence1: Most pituitary hormones control other endocrine glands. 
Sentence2: Endocrine glands include the pituitary, thyroid, parathyroid, adrenal, pineal and thymus glands.
Example Output:
endocrine