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: Fish are the first known true chordates. 
Sentence2: Fish are the first known animal with a backbone.

SOLUTION: Fish

PROBLEM: Sentence1: pathogens can cause disease. 
Sentence2: pathogens affects the immune system.

SOLUTION: pathogens

PROBLEM: Sentence1: a radio converts electrical energy into vibrations. 
Sentence2: electrical energy turns into vibrations.

SOLUTION:
vibrations