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: DNA is made up of nucleotides.
Sentence2: Mutations can change the structure of DNA.
Example Output: DNA

Example Input: Sentence1: Excretion is the process of removing wastes and excess water from the body.
Sentence2: parasites remove waste from their bodies.
Example Output: wastes

Example Input: Sentence1: Blood pH may become unbalanced if the rate of breathing is too fast or too slow.
Sentence2: Normal human blood may become unbalanced if the rate of breathing is too fast or too slow.
Example Output:
become