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: creating paper requires cutting down trees. 
Sentence2: Trees begin as epiphytes on host trees.

SOLUTION: trees

PROBLEM: Sentence1: Babies that are very large or very small at birth are less likely to survive. 
Sentence2: Babies that are very large or very small at birth are less likely to live.

SOLUTION: Babies

PROBLEM: Sentence1: temperature changing can cause phase changes. 
Sentence2: Temperature changing can cause potential energy changes.

SOLUTION:
cause