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: An organism can gain energy by assimilation or absorption of food. 
Sentence2: Organisms require food for growth.
Example Output: food

Example Input: Sentence1: a magnet moving in a coil of copper wire can cause an electric current. 
Sentence2: An electric current forms when a magnet is run through an induction coil.
Example Output: current

Example Input: Sentence1: Oxidation of iron minerals causes the redness of the rocks. 
Sentence2: chemical weathering causes redness of the rocks containing iron.
Example Output:
iron