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: Antibodies are large, Y-shaped proteins that recognize and bind to antigens. 
Sentence2: Some of the antibodies, antophospholipid antibodies, cause blood clots.
Example Output: Antibodies

Example Input: Sentence1: when a hemisphere is tilted away from the sun , that hemisphere receives less direct sunlight. 
Sentence2: Sunlight is delivered in small packets of energy called photons.
Example Output: sunlight

Example Input: Sentence1: if the amount of available food and water decreases in an environment then animals may leave that environment to find food and water. 
Sentence2: All humans are animals.
Example Output:
animals