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: Lions live in social groups called prides. 
Sentence2: Chimpanzees live in social groups called communities.

SOLUTION: groups

PROBLEM: Sentence1: Rainy clouds cause rain, and excess water vapor from clouds is the basis of rainbows. 
Sentence2: Condensation can lead to rain.

SOLUTION: rain

PROBLEM: Sentence1: eyes are used for seeing by animals by sensing light. 
Sentence2: Visible and invisible light is energy in the form of electromagnetic waves.

SOLUTION:
light