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.

Q: Sentence1: Mammals that are viviparous are called therian mammals. 
Sentence2: Mouse-sized viviparous mammals evolved by Jurassic times.

A: Mammals
****
Q: Sentence1: Capillaries are microscopic vessels. 
Sentence2: Lymph is a fluid that leaks out of microscopic vessels into spaces between cells.

A: microscopic
****
Q: Sentence1: The Caspian Sea is, strictly speaking, not really a sea but instead the world's largest lake. 
Sentence2: The Caspian Sea was formed by precipitation and runoff.

A:
Caspian
****