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: Animals can communicate with sounds, chemicals, or visual cues. 
Sentence2: cats can communicate with sounds, chemicals or visual cues.
Example Output: chemicals

Example Input: Sentence1: Leeches are external parasites. 
Sentence2: Leeches live on the surface of their hosts.
Example Output: Leeches

Example Input: Sentence1: Chloroplasts are organelles that are found in the cells of plants and algae. 
Sentence2: pigments are found in algae.
Example Output:
algae