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: June Summer Triangle Three bright stars light up the summer sky. 
Sentence2: Nuclear reactions in stars cause them to brighten up the summer sky.

SOLUTION: bright

PROBLEM: Sentence1: Herbs are medicines and aids. 
Sentence2: herbs are used for curing people when they are sick.

SOLUTION: Herbs

PROBLEM: Sentence1: Stomata opening are controlled by guard cells. 
Sentence2: Guard cells are needed to reduce water loss.

SOLUTION:
cells