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: when a gas in an open container evaporates , that gas spreads out into the air. 
Sentence2: If you place gas in an open box it will evaporate and spread out into the air.
gas

Sentence1: when a body of water receives more water than it can hold , a flood occurs. 
Sentence2: Floods are deadly, floods are devastating.
flood

Sentence1: Female gametes are called eggs. 
Sentence2: Adult sponges produce female gametes and sperm.

Female