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: Flies are insects with two wings. 
Sentence2: Flies are arthropods with two wings.
Flies

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

Sentence1: Silica sand is primarily mined from sandstone deposits. 
Sentence2: erosion forms silica sand.

Silica