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: erosion causes a river to become deeper and wider. 
Sentence2: On the contrary, the NILE is the longest river in Africa.

Answer: river


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: Organic matter is the plant and animal residue in the soil at various stages of decomposition. 
Sentence2: Plant and animal residue increases the amount of nutrients in the soil.

Answer:
and