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: Plants that shed their leaves seasonally each year are called deciduous plants. 
Sentence2: vines shed their leaves seasonally each year.
Example Output: each

Example Input: Sentence1: if an organism becomes too hot then that organism may die. 
Sentence2: a plant can collapse if it gets too hot.
Example Output: hot

Example Input: Sentence1: heat and pressure change the remains of prehistoric living things into natural gas. 
Sentence2: Heat and pressure turns plants into gas.
Example Output:
heat