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

Sentence1: if an object is made of a material then that object has the properties of that material. 
Sentence2: items properties are the same as the materials the item is made of.
made

Sentence1: Communities consist of populations of different species. 
Sentence2: Within any species, there is genetic diversity.

species