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: Dilation occurs when cell walls relax. 
Sentence2: Decreased oxygen levels cause blood vessels to dilate and cell walls to relax.
relax

Sentence1: Angiosperm sporophyte is dominant. 
Sentence2: Flowers form on angiosperms.
Angiosperm

Sentence1: Pneumonia may be caused by an infection or injury of the lungs. 
Sentence2: Smoke inhalation and thermal lung injury cause direct lung injury.

injury