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: sharpening an object causes that object to change shape.
Sentence2: sharpening a knife causes it to change shape.
Example Output: causes

Example Input: Sentence1: faulting of rock in Earth 's crust causes earthquakes.
Sentence2: Fault zones are plates in the earth that slide and collide.
Example Output:
faulting