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: Protozoa make humans sick when they become human parasites. 
Sentence2: paramecium are single celled animals that make humans sick when they become human parasites.

A: become
****
Q: Sentence1: Mitosis is cell division. 
Sentence2: mitosis often causes growth.

A: Mitosis
****
Q: Sentence1: Corals form large colonies in shallow tropical water. 
Sentence2: Corals form large colonies in shallow warm waterways.

A:
Corals
****