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

SOLUTION: pathogens

PROBLEM: Sentence1: Faster metabolism means more calories consumed, and usually, weight loss. 
Sentence2: mammals generate heat by consuming calories.

SOLUTION: calories

PROBLEM: Sentence1: Insects are just part of the Arthropod subdivision. 
Sentence2: arthropods can spread disease and destroy crops.

SOLUTION:
Arthropod