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: boiling means change from a liquid into a gas by adding heat energy. 
Sentence2: boiling changes a liquid into steam.
liquid

Sentence1: ultraviolet light causes sunburn. 
Sentence2: Sunburn risk is higher at elevation.
sunburn

Sentence1: Algae have varied life cycles. 
Sentence2: algae are capable of reproduction.

Algae