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 a habitat can no longer support animals then those animals will move to another area. 
Sentence2: Each species of animal is unique.
Example Output: animals

Example Input: Sentence1: healing requires rest. 
Sentence2: Healing and cell regeneration follows.
Example Output: healing

Example Input: Sentence1: Vinegar, battery acid, and wine are acids. 
Sentence2: Acids can cause harm to the eyes.
Example Output:
acids