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: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: humans have collected and grown porcinis for thousands of years.

SOLUTION: Humans

PROBLEM: Sentence1: erosion of soil has a negative impact on the environment. 
Sentence2: erosion of soil has a negative impact on forests.

SOLUTION: erosion

PROBLEM: Sentence1: Complex chemistry is needed to carry out all the functions of life. 
Sentence2: Chemistry is primarily concerned with matter, energy, and their interactions.

SOLUTION:
chemistry