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: Habitat destruction is the primary cause of extinction or threat of extinction for all animals. 
Sentence2: building housing developments may cause extinction.
extinction

Sentence1: Plants use unsaturated fatty acids to store energy. 
Sentence2: Plants and fish contain fatty acids.
Plants

Sentence1: condensing means changing from a gas into a liquid by reducing heat energy. 
Sentence2: Changing water vapor to a liquid is done by reducing heat energy.

changing