Sentence:  [<WSD>N</WSD>]<WSD>itrox</WSD> is often referred to as ‘enriched air' or ‘enriched air – <WSD>nitrox</WSD>' (EANx). By convention, the mix is described by reference to its oxygen content. Thus, if a <WSD>nitrox</WSD> mix contains 36 per cent oxygen, then it is referred to as ‘<WSD>nitrox</WSD> 36' (‘Nx36') or ‘EANx36'. [...] [T]he <WSD>nitrox</WSD> diver can use the reduced absorption of nitrogen to increase allowable dive time by using the EAD to derive the no-decompression limit for the dive or as a basis for calculating decompression. This approach allows longer dives and shorter decompression. 
Meaning of the word marked with <WSD> tags:  A mixture of nitrogen and oxygen, the nitrogen content being lower than what is normally present in air, which is used in place of air as a breathing gas.