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: waxy leaves are used for storing water by some plants. 
Sentence2: waxy leaves are used for water conservation by some plants.
Example Output: leaves

Example Input: Sentence1: bacteria can cause people to become ill. 
Sentence2: Signs of bacteria-related illness include nausea and diarrhea.
Example Output:
ill