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: Mollusks are invertebrates such as the common snail. 
Sentence2: snails have no backbone.
snail

Sentence1: Combustion-related, motor vehicles, wood burning, open burning, industrial processes. 
Sentence2: Combustion is used to produce heat.
Combustion-related

Sentence1: Competition may lead to aggressive behaviors or displays of aggression. 
Sentence2: Human mating may lead to aggressive behaviors or displays of aggresion.

aggression