TASK DEFINITION: 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.
PROBLEM: Sentence1: All cells share some of the same structures and basic functions. 
Sentence2: Inside the cell is a structure called the nucleus.

SOLUTION: cells

PROBLEM: Sentence1: Bound and free ribosomes are structurally identical and interchangeable. 
Sentence2: Bound and free structures are in the cytoplasm where proteins are made.

SOLUTION: Bound

PROBLEM: Sentence1: Bryophytes are mosses, liverworts, and hornworts. 
Sentence2: Most in the same group as mosses are small.

SOLUTION:
mosses