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.

Sentence1: Metabolic rate is the rate at which food is burned for energy. 
Sentence2: thyroid hormones increase the rate of energy consumption.
energy

Sentence1: Precipitation falls on the windward side of the mountain range. 
Sentence2: Sheep tend to favour the windward side of a paddock.
windward

Sentence1: The results of a planet's rotation is its length of day. 
Sentence2: a planet has cycles caused by rotation.

rotation