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.

Sentence1: cell division often causes growth. 
Sentence2: Cell division leads to reproduction.
cell

Sentence1: Methane gas is a produced by rotting compost, trash, and human waste. 
Sentence2: Methane gas can be produced by Slime molds.
Methane

Sentence1: the Himalayas were formed by rock folding. 
Sentence2: The Himalayas were formed by earthquakes.

Himalayas