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.

Input: Consider Input: Sentence1: Combustion-related, motor vehicles, wood burning, open burning, industrial processes. 
Sentence2: Combustion is used to produce heat.

Output: Combustion-related


Input: Consider Input: Sentence1: a sifter is used for separating mixtures. 
Sentence2: a sifter is used for some recipes.

Output: sifter


Input: Consider Input: Sentence1: Insects are the largest group of arthropods. 
Sentence2: Insects belong to the largest phylum of invertibrates.


Output: Insects