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: Very often their only metal object in the house is a cooking pot or a knife. 
Sentence2: sharpening a knife causes it to change shape.
knife

Sentence1: Genetics is the study of inheritance. 
Sentence2: Pedigrees are useful tools for studying genetics.
Genetics

Sentence1: a generator converts kinetic energy into electrical energy. 
Sentence2: a generator can convert kinetic energy into light.

converts