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: Chordates have a complete digestive system and a closed circulatory system. 
Sentence2: animals with jaws have a complete digestive system and a closed circulatory system.
circulatory

Sentence1: An astronaut is a scientist who is a space explorer. 
Sentence2: Space explorers require preserved food for long flights.
explorer

Sentence1: Annelids are worms such as the familiar earthworm. 
Sentence2: Annelids include earthworms and leeches.

Annelids