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: All lizards are reptiles. 
Sentence2: Lizards are tetrapod vertebrates that produce amniotic eggs.
lizards

Sentence1: a plant requires sunlight to grow. 
Sentence2: Grass needs air and sunlight.
sunlight

Sentence1: Ice ages buried the planet in snow and ice for millions of years at a time. 
Sentence2: something rare in geologic history buried the planet in snow for millions of years.

millions