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: Mitosis is cell division. 
Sentence2: mitosis often causes growth.
Mitosis

Sentence1: Blood is a fluid connective tissue. 
Sentence2: A fluid connective tissue carries oxygen to the brain.
connective

Sentence1: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: Mushrooms are a fungus and have no chlorophyll.

mushrooms