TASK DEFINITION: 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.
PROBLEM: Sentence1: Light source is an ultra-bright, unbreakable LED Bulb. 
Sentence2: LEDs convert electricity into light and heat energy.

SOLUTION: LED

PROBLEM: Sentence1: a flashlight converts chemical energy into light energy. 
Sentence2: Chemical energy converted to light energy requires batteries.

SOLUTION: chemical

PROBLEM: Sentence1: the gravitational pull of the Moon on Earth 's oceans causes the tides. 
Sentence2: The tide causes erosion.

SOLUTION:
causes