instruction:
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.
question:
Sentence1: Mating is generally preceded by courtship. 
Sentence2: Mating is generally similar across species.
answer:
Mating


question:
Sentence1: an earthquake causes the ground to shake. 
Sentence2: A number of buildings in Istanbul also were damaged in the earthquake.
answer:
earthquake


question:
Sentence1: Sound vibrations travel at different speeds through different materials. 
Sentence2: Sound moves through different materials at different rates.
answer:

different