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: Acids dissolve in base and turn blue litmus red. 
Sentence2: acid changes color.
Acids

Sentence1: Heat and temperature are the same. 
Sentence2: a thermometer is used to measure heat.
Heat

Sentence1: Car and automobile, for example, are synonyms. 
Sentence2: operating a car usually requires fossil fuels.

Car