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: Telephone Telephone calls are expensive. 
Sentence2: Communicating by transmitting sound is expensive.
expensive

Sentence1: bacteria cause food to spoil. 
Sentence2: Food poisoning occurs when spoiled food is eaten.
spoil

Sentence1: Bacteria are very small. 
Sentence2: Biologists use microscopes to see bacteria.

Bacteria