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: Light source is an ultra-bright, unbreakable LED Bulb. 
Sentence2: LEDs convert electricity into light and heat energy.
Example Output: LED

Example Input: Sentence1: Silica sand is primarily mined from sandstone deposits. 
Sentence2: erosion forms silica sand.
Example Output: Silica

Example Input: Sentence1: Most reptiles have good eyesight and a keen sense of smell. 
Sentence2: Most animals in the class reptilia have good eyesight and a keen sense of smell.
Example Output:
Most