Part 1. 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.
Part 2. Example
Sentence1: pesticides cause pollution. 
Sentence2: pollution can harm animals.
Answer: pollution.
Explanation: The word "pollution" is common to Sentence1 and Sentence2. So, it's a good answer.
Part 3. Exercise
Sentence1: Prokaryotes are single-celled organisms that lack a nucleus. 
Sentence2: Prokaryotes have no membrane-bound organelles, thus bacteria are prokaryotic organisms.
Answer:
Prokaryotes