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: a thermometer is used to measure temperature. 
Sentence2: a thermometer is used to measure heat.

SOLUTION: a

PROBLEM: Sentence1: a flashlight converts chemical energy into light energy. 
Sentence2: Only as long as there are batteries in the flashlight, the flashlight will function.

SOLUTION: flashlight

PROBLEM: Sentence1: Adult sponges are sessile. 
Sentence2: Adult sponges attach to a substrate.

SOLUTION:
Adult