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: Runoff water is wasted water. 
Sentence2: Streams may start with wasted water.

SOLUTION: wasted

PROBLEM: Sentence1: Flatworms Flatworms or Platyhelminthes include flukes, tapeworms, and turbellarians. 
Sentence2: Tapeworms belong to the phylum Platyhelminthes.

SOLUTION: tapeworms

PROBLEM: Sentence1: Differentiation is the process by which unspecialized cells become specialized. 
Sentence2: Unspecialized cells are the only ones that are naturally vulnerable to cancer.

SOLUTION:
unspecialized