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.

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

Sentence1: Producers use energy and inorganic molecules to make food. 
Sentence2: Green plants use energy and inorganic molecules to make food.
energy

Sentence1: Vertebrates are animals that have a backbone. 
Sentence2: Vertebrates are animals that have trunk muscles.

Vertebrates