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: An accounting period is simply a period of time. 
Sentence2: seconds are used to measure a period.

SOLUTION: period

PROBLEM: Sentence1: an animal requires warmth for survival. 
Sentence2: Light and heat and warmth are basic necessities for survival.

SOLUTION: warmth

PROBLEM: Sentence1: a vehicle is used for transportation. 
Sentence2: Trailers and boats are counted as a private vehicles.

SOLUTION:
vehicle