This is the 720th most frequent Russian word.
нефти
"Нефти" means "oil" or "petroleum" in English.
Here, 'нефти' is used in the genitive singular form to indicate an amount of oil being exported. It specifies the type of substance in question.
Россия экспортирует много нефти.
Russia exports a lot of oil.
In this case, 'нефти' appears in the genitive singular form as part of the phrase 'цены на нефти,' meaning 'prices of oil,' indicating the subject of the price.
Цены на нефти повышаются.
The prices of oil are rising.
Here, the word 'нефти' is used in its genitive singular form, related to the action (refining), showing possession or association with the substance being processed.