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.

Q: Sentence1: Mitosis is cell division. 
Sentence2: Chromosomes are the form of the genetic material of a cell during mitosis.

A: Mitosis
****
Q: Sentence1: Thrinaxodon, a small Lystrosaurus Zone cynodont, shows many of the characters of the group. 
Sentence2: Thrinaxodon is from the animal family that eventually evolved into mammals.

A: Thrinaxodon
****
Q: Sentence1: lightning can cause a forest fire. 
Sentence2: Forest fires are bad for the environment.

A:
fire
****