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.

Example Input: Sentence1: if an object is black then that object absorbs all visible light. 
Sentence2: Something is black if it absorbs visible light and doesn't reflect.
Example Output: light

Example Input: Sentence1: Cultivation is easier if soil is loose. 
Sentence2: soil with more oxygen is easier to cultivate.
Example Output: Cultivation

Example Input: Sentence1: Life's main property is the ability to reproduce. 
Sentence2: Complex chemistry is needed to carry out all the functions of that which can reproduce.
Example Output:
reproduce