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.
Input: Sentence1: Immunodeficiency occurs when the immune system is not working properly. 
Sentence2: immunodeficiency causes people to take longer to get well.

Immunodeficiency