This is the 1237th most frequent Russian word.
нефть
Oil (petroleum).
The use of 'нефть' here represents the substance 'oil' as a natural resource found in reservoirs.
На месторождении обнаружили новые запасы нефти.
New oil reserves were discovered at the field.
'нефть' in this sentence refers to oil as a traded commodity affecting economic markets.
Цена на нефть повышается из-за роста спроса.
The price of oil is rising due to increased demand.
Here, 'нефть' signifies crude oil undergoing industrial processes for refinement.