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: Sponges are filter feeders. 
Sentence2: Hawksbills feed primarily on filter feeders.

SOLUTION: feeders

PROBLEM: Sentence1: Ions are atoms or groups of atoms that carry a positive or negative electrical charge. 
Sentence2: An ion is formed after a neutral atom loses an electron.

SOLUTION: Ions

PROBLEM: Sentence1: A battery is a store of chemical energy. 
Sentence2: batteries store chemicals.

SOLUTION:
chemical