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: a flashlight requires a source of electricity to produce light. 
Sentence2: Flashlights provide the safest emergency lighting source.
Example Output: flashlight

Example Input: Sentence1: Insects have 2 antennae. 
Sentence2: Insects have 2 appendages to detect sound.
Example Output: 2

Example Input: Sentence1: Most of the yard lamps are incandescent. 
Sentence2: most yard lamps convert electricity to light using a filament.
Example Output:
Most